Материал: part17

FFF.2.5.1.3.4 X-Ray Field of View Macro Recommendations​

The usage of this macro is recommended to specify the characteristics of the field of view.​

The field of view characteristics may change per-frame across the Multi-frame Image.​

FFF.2.5.1.3.5 X-Ray Isocenter Reference System Macro Recommendations​

The usage of this macro is recommended to specify the fixed reference system of the acquisition geometry.​

FFF.2.5.1.3.6 X-Ray Geometry Macro Recommendations​

The usage of this macro is recommended to specify the distances between the X-Ray source, isocenter and X-Ray detector.​

FFF.2.5.1.3.7 XA/XRF Frame Pixel Data Properties Macro Recommendations​

The usage of this macro is recommended to specify the dimensions of the pixels at the image reception plane.​

FFF.2.5.1.4 Example​

In this example, the operator identifies the position (i, j) of an object of interest projected on the stored pixel data of an image A, and​ estimates the magnification of the conic projection by a calibration process.​

The operator wants to know the position of the projection of such object of interest on a second image B acquired under different​ geometry.​

The Attributes that define the geometry of both images A and B are described in the following figure:​

- Standard -​

Figure FFF.2.5-1. Attributes of the example of tracking an object of interest on multiple 2D images​

The following steps describe the process to calculate the position (i, j)B of the projection of the object of interest in the Pixel Data of​ the image B, assuming that (i, j)A is known and is the offset of the projection of the object of interest from the TLHC of the Pixel Data​ of the image A, measured in pixels of the Pixel Data matrix as a column offset "i" followed by a row offset "j". TLHC is defined as (0,0).​

Step 1: Calculate the point (i, j)A in FOV coordinates of the image A.​

Step 2: Calculate the point (i, j)A in physical detector coordinates of the image A.​

Step 3: Calculate the point (Pu, Pv)A in positioner coordinates of the image A.​

Step 4: Calculate the point (PXp, PYp, PZp)A in positioner coordinates of the image A.​

Step 5: Calculate the point (PX, PY, PZ)A in Isocenter coordinates of the image A.​

Step 6: Calculate the point (PXt, PYt, PZt)A in Table coordinates of the image A.​

Step 7: Calculate the point (PXt, PYt, PZt)B in Table coordinates in mm of the image B.​

Step 8: Calculate the point (PX, PY, PZ)B in Isocenter coordinates in mm of the image B.​

Step 9: Calculate the point (PXp, PYp, PZp)B in positioner coordinates of the image B.​

- Standard -​

Step 10: Calculate the point (Pu, Pv)B in positioner coordinates of the image B.​

Step 11: Calculate the point (i, j)B in physical detector coordinates of the image B.​

Step 12: Calculate the point (i, j)B in FOV coordinates of the image B.​

Step 13: Calculate the point (i, j)B in Pixel Data of the image B.​

In this example let's assume:​

(i, j)A = (310,122) pixels​

Magnification ratio = 1.3​

Step 1 : Image A: Point (i, j)A in FOV coordinates​

In this step, the FOV coordinates are calculated by taking into account the FOV rotation and Horizontal Flip applied to the FOV matrix​ when the Pixel Data were created:​

1.1: Horizontal Flip: YES​

new i = (columns -1) - i = 850 - 1 - 310 = 539​

new j = j = 122​

1.2: Image Rotation: 90 (clockwise)​

new i = j = 122​

new j = (columns -1) - i = 850 - 1 - 539 = 310​

(i, j)A = (122, 310) in stored pixel data.​

Step 2: Image A: Point (i, j)A in physical detector coordinates​

In this step, the physical detector coordinates are calculated by taking into account the FOV origin and the ratio between Imager Pixel​

Spacing and Detector Element Spacing:​

Di = Imager Pixel Spacing (column) = 0.2 mm​

Dj = Imager Pixel Spacing (row) = 0.2 mm​

Didet = Detector Element Spacing between two adjacent columns = 0.2 mm​

Djdet = Detector Element Spacing between two adjacent rows = 0.2 mm​

Zoom Factor (column) = Di / Didet = 1.0​

Zoom Factor (row) = Dj / Djdet = 1.0​

FOV Origin (column) = FOVidet = 600.0​

FOV Origin (row) = FOVjdet = 600.0​

new i = FOVidet + (i + (1 - Didet / Di) / 2) * Dj / Djdet = 600 + 122 * 1.0 = 722​ new j = FOVjdet + (j + (1 - Djdet / Dj) / 2) * Di / Didet = 600 + 310 * 1.0 = 910​

(i, j)A = (722, 910) in detector elements.​

Step 3: Image A: Point ( Pu, Pv)A in positioner coordinates​

In this step, the (Pu, Pv)A coordinates in mm are calculated from (i, j)A by taking into account the projection of the Isocenter in physical​ detector coordinates, and the Detector Element Spacing:​

- Standard -​

ISO_Pidet = Position of Isocenter Projection (column) = 1024.5​

ISO_Pjdet = Position of Isocenter Projection (row) = 1024.5​

Didet = Detector Element Spacing between two adjacent columns = 0.2 mm​

Djdet = Detector Element Spacing between two adjacent rows = 0.2 mm​

Pu = (i - ISO_Pidet) * Didet = (722 - 1024.5) * 0.2 = -60.5 mm​

Pv = (ISO_Pjdet - j) * Djdet = (1024.5 - 910) * 0.2 = 22.9 mm​

( Pu, Pv)A = (-60.5, 22.9) in mm.​

Step 4: Image A: Point (PXp, PYp, PZp)A in positioner coordinates​

In this step, the positioner coordinates (PXp, PYp, PZp)A are calculated from (Pu, Pv)A by taking into account the magnification ratio,​ the Distance Source to Detector and the Distance Source to Isocenter:​

SID = Distance Source to Detector = 1300 mm​

ISO = Distance Source to Isocenter = 780 mm​

Magnification ratio = SID / (ISO - P Yp ) = 1.3​

PYp = ISO - SID / 1.3 = 780 - 1300/1.3 = -220 mm​

PXp = Pu / Magnification ratio = -60.5 / 1.3 = -46.54 mm​

PZp = Pv / Magnification ratio = 22.9 / 1.3 = 17.62 mm​

(PXp, PYp, PZp)A = (-46.54, -220, 17.62) in mm.​

Step 5: Image A: Point (PX, PY, PZ)A in Isocenter coordinates​

Inthisstep,theisocentercoordinates(PX,PY,PZ)A arecalculatedfromthepositionercoordinates(PXp,PYp,PZp)A bytakingintoaccount​ the positioner angles of the image A in the Isocenter coordinate system:​

Ap1 = Positioner Isocenter Primary Angle = 60.0 deg​

Ap2 = Positioner Isocenter Secondary Angle = 20.0 deg​

Ap3 = Positioner Isocenter Detector Rotation Angle = 0.0 deg​ (PX, PY, PZ)T= (R2 ·R1)T·(R3 T·(PXp, PYp, PZp)T)​

(PX, PY, PZ)A = (150.55, -65.41, 91.80) in mm.​

Step 6: Image A: Point (PXt, PYt, PZt)A in Table coordinates​

In this step, the table coordinates (PXt, PYt, PZt)A are calculated from the isocenter coordinates (PX, PY, PZ)A by taking into account​ the table position and angles of the image A in the Isocenter coordinate system:​

Tx =Table X Position to Isocenter = 10.0 mm​

Ty =Table Y Position to Isocenter = 30.0 mm​

Tz =Table Z Position to Isocenter = 100.0 mm​

At1 = Table Horizontal Rotation Angle = -10.0 deg​

At2 = Table Head Tilt Angle = 0.0 deg​

At3 = Table Cradle Tilt Angle = 0.0 deg​

- Standard -​

(PXt, PYt, PZt)T= (R3 · R2 · R1) · ((PX, PY, PZ)T- (TX, TY, TZ)T)​

(PXt, PYt, PZt)A = (136.99, -95.41, -32.48) in mm.​

Step 7: Image B: Point (PXt, PYt, PZt)B in Table coordinates​

In this step, the table has moved from image A to image B. The table coordinates of the object of interest are the same on image A​ and image B because it is assumed that the patient is fixed on the table.​

(PXt, PYt, PZt)B = (136.99, -95.41, -32.48) in mm.​

Step 8: Image B: Point (PX, PY, PZ)B in Isocenter coordinates​

In this step, the isocenter coordinates (PX, PY, PZ)B are calculated from the table coordinates (PXt, PYt, PZt)B by taking into account​ the table position and angles of the image B in the Isocenter coordinate system:​

Tx =Table X Position to Isocenter = 20.0 mm​

Ty =Table Y Position to Isocenter = 100.0 mm​

Tz =Table Z Position to Isocenter = 0.0 mm​

At1 = Table Horizontal Rotation Angle = 0.0 deg​

At2 = Table Head Tilt Angle = 10.0 deg​

At3 = Table Cradle Tilt Angle = 0.0 deg​

(PX, PY, PZ)T= (R3 · R2 · R1)T· (PXt, PYt, PZt)T+ (TX, TY, TZ)T​

(PX, PY, PZ)B = (156.99, -12.11, -48.55) in mm.​

Step 9: Image B: Point (PXp, PYp, PZp)B in positioner coordinates​

Inthisstep,thepositionercoordinates(PXp,PYp,PZp)B arecalculatedfromtheisocentercoordinates(PX,PY,PZ)B bytakingintoaccount​ the positioner angles of the image B in the Isocenter coordinate system:​

Ap1 = Positioner Isocenter Primary Angle = -30.0 deg​

Ap2 = Positioner Isocenter Secondary Angle = 0.0 deg​

Ap3 = Positioner Isocenter Detector Rotation Angle = 0.0 deg​

(PXp, PYp, PZp)T= R3 · ((R2 · R1) · (PX, PY, PZ)T)​

(PXp, PYp, PZp)B = (142.01, 68.00, -48.55) in mm.​

Step 10: Image B: Point ( Pu, Pv)B in positioner coordinates​

In this step, the (Pu, Pv)B coordinates in mm are calculated from the positioner coordinates (PXp, PYp, PZp)B by taking into account​ the Distance Source to Detector and the Distance Source to Isocenter of the image B:​

- Standard -​