Thorax Phantom
Author: Katia Sourbelle

A modification of the thorax FORBILD phantom for 4D imaging by Frank Bergner, Marc Kachelrieß is available here.

 

 

Figure 1: Representation of the bones of the Thorax Phantom.

Aims

To provide semi–anthropomorphic cone–beam rawdata for CT-examinations of the thorax.

Phantom Description

The Phantom should represent the important parts of the thorax which are usually visualised during the CT examination : lungs, heart, aorta, ribs, spine, sternum, and shoulders.

Thorax:

The lungs are represented by two ellipsoids and the heart by a sphere. The aorta consists of three joined cylinders (2 vertical and 1 horizontal), to represent its ascending and descending parts.

The ribs will be modelled by nine small joined cylinders (Fig 2.a). In order to define the cylinders, we will say that their center lies on a tilted ellipse with the co-ordinates {a cos(q ), b sin(q ), c sin(q )}, for q between p /2 and 3p /2 with steps of p /10. The axes of the cylinders are parallel to the tangent of the ellipse at the centers.
We will take 5*2 ribs for the whole thorax.

For the spine we use the model defined for the Cardio-Phantom (Stefan Ulzheimer, IMP) which will be built to evaluate the quality of CT images (Fig 2.b).

The Sternum will be represented by a box.

wpeA0.jpg (11668 Byte)

Figure 2: a)Rib consisting of nine cylinders aligned along a tilted ellipse. b)Model of the vertebra used for the Cardio-Phantom

wpeA1.jpg (11738 Byte)

Figure 3: Slice of the Phantom at z = 0, showing the different parts of the thorax. 1:lung, 2:heart, 3:sternum, 4:vertebra, 5:aorta, 6:rib. Image Size 40cm*40cm.

 

Shoulders:

The clavicle is represented by a cylinder and the shoulder blade by the half of an ellipse. In order to simulate the usual stark attenuation at the shoulders, we will modell them by two spheres.

 

wpeA3.jpg (10864 Byte)

Figure 4: Slice of the phantom at z =15, showing the modelling of the shoulders. 1:humerus, 2:clavicle, 3:sternum, 4:shoulder blade, 5:vertebra. Image Size 50cm*50cm

All bones are filled with marrow. The whole Phantom will be made of 271 basic objects. The exact definition of the phantom are given in the following tables. The units are cm for the lengths and g/cm3 for the densities. The relevant objects lie between z=-15 cm and z=+18 cm. The field of view is 50 cm.

 

  Object Center Axis Parameters Clip plane Density
Thorax Cylinder [0, 0, 0] [0, 0, 1] L=50 ax=20 ay=10   1.000
Arm L Cylinder [-20, 0, 17.5] [0, 0, 1] L=15 R=5   1.000
Arm R Cylinder [20, 0, 17.5] [0, 0, 1] L=15 R=5   1.000
Lunge L Ellipsoid [-10.5, 0, 0]   ax=7.5 ay=5.5 az=15   0.260
Lunge R Ellipsoid [10.5, 0, 0]   ax=7.5 ay=5.5 az=15   0.260
Heart Shere [0, 4, 0]   R=3.5   1.050
Sternum Box

Box

[0, 9, 2.5]

[0, 9, 2.5]

  Lx=2.5 Ly=0.8 Lz=25

Lx=2 Ly=0.5 Lz=25

  1.250

0.980

Clavicle L Cylinder

Cylinder

[-10, 5.5, 16]

[-10, 5.5, 16]

[20, 9, -2]

[20, 9, -2]

L=17 R=0.5

L=16.5 R=0.4

  1.460

0.980

Clavicle R Cylinder

Cylinder

[10, 5.5, 16]

[10, 5.5, 16]

[20, -9, 2]

[20, -9, 2]

L=17 R=0.5

L=16.5 R=0.4

  1.460

0.980

Shoulder blade L Ellipsoid_free

 

Ellipsoid_free

[-12 ,-5, 15]

 

[-12 ,-5, 15]

Ax[2,-1, 0]

Ay[1, 2, 0]

Ax[2,-1, 0]

Ay[1, 2, 0]

ax=4.5 ay=0.5 az=6

 

ax=4 ay=0.4 az=5.5

Z<15 1.460

 

0.980

Shoulder blade R Ellipsoid_free

 

Ellipsoid_free

[12 ,-5, 15]

 

[12 ,-5, -15]

Ax[2, 1, 0]

Ay[-1, 2, 0]

Ax[2,-1, 0]

Ay[1, 2, 0]

ax=4.5 ay=0.5 az=6

 

ax=4 ay=0.4 az=5.5

Z<15 1.460

 

0.980

Humerus L Sphere

Sphere

Sphere

Sphere

[-22, 0, 15]

[-16.5, 0, 15]

[-22, 0, 15]

[-16.5, 0, 15]

  R=2.5

R=2.5

R=2

R=2

  1.460

1.460

0.980

0.980

Humerus R Sphere

Sphere

Sphere

Sphere

[22, 0, 15]

[16.5, 0, 15]

[22, 0, 15]

[16.5, 0, 15]

  R=2.5

R=2.5

R=2

R=2

  1.460

1.460

0.980

0.980

Aorta Cylinder

Cylinder

 

Cylinder

[-2.5, -2.5, 0]

[-1, 1, 7.5]

 

[-0.5, 4.5, 6]

[0, 0, 1]

[3, 7, 0]

 

[0, 0, 1]

L=30 R=1

L=20 R=1

 

L=6 R=1

R(3,7,7.615)<2.982

R(3,7,7.615)>2.982

R(1, 2, -2.236)<-2.239

R(1, 2, -2.236) >-2.239

1.050

1.050

 

1.050

Table 1: Definition of the different parts of the phantom

 

Object Center Axis Param Clip plane density
Cylinder [X, Y, Z] [0, 0, 1] L=2 R=1.75   1.920
Box [X, Y-1.4, Z]   Lx=2.343 Ly=0.2 Lz=2   1.920
Cylinder [X, Y, Z] [0, 0, 1] L=2 R=1.5   1.180
Box [X-2, Y-1.975, Z]   Lx=4 Ly=0.95 Lz=2 R(-0.95, 2.828, 0) < -1.04893-0.318392 +0.947959 Y

R(-2, 32, 0) > -2.19572-0.0623783 X+0.998053 Y

1.920
Box [X+2, Y-1.975, Z]   Lx=4 Ly=0.95 Lz=2 R(-0.95, 2.828, 0) < -1.04893 +0.318392 +0.947959 Y

R(2, 32, 0)> -2.19572 +0.0623783 X +0.998053 Y

1.920
Box [X, 2.35+Y, Z]   Lx=1.6 Ly=0.3 Lz=2 R(-2,4,0)> -2.37023 -0.447214 X +0.894427 Y

R(-2,-4,0)< 2.37023 -0.447214 X -0.894427 Y

1.920
Box [X, -3.25+Y, Z]   Lx=0.8 Ly=1.6 Lz=2   1.920
Cylinder [X, Y-4.05, Z] [0, 0, 1] L=17 R=0.5 Y < Y-4.05 1.920

Table 2: Definition of a vertebra at the position (X, Y, Z)

The phantom consists of 9 vertebras placed at X=0, Y=-5 and Z between –6 and 15.

 

The ribs lie on the ellipse of parameters a=-18.5, b=9, c=-5.5 .

All the cylinders composing a rib have a radius of 0.5. The inner cylinders for the marrowbone have a radius of 0.4.

Center Axis Clip plane density
x=5.716814

y=8.559509

z=-5.230811

17.594546

-2.781153

1.699593

r(1.907146,-0.481971,0.294538 ) <5.451355

r(1.983271,-0.155425,0.094982 ) >1.953178

1.410 / 0.980
x=10.874027

y=7.281153

z=-4.449593

14.966814

-5.290067

3.232819

r(1.710571,-0.853311,0.521468 ) <7.622861

r(1.907146,-0.481971,0.294538 ) >5.451355

1.410 / 0.980
x=14.966814

y=5.290067

z=-3.232819

10.874027

-7.281153

4.449593

r(1.281833,-1.268109,0.774956 ) <7.228981

r(1.710571,-0.853311,0.521468 ) >7.622861

1.410 / 0.980
x=17.594546

y=2.781153

z=-1.699593

5.716814

-8.559509

5.230811

r(0.495137,-1.594626,0.974494 ) <3.123195

r(1.281833,-1.268109,0.774956 ) >7.228981

1.410 / 0.980
x=18.500000

y=-0.000000

z=0.000000

-0.000000

-9.000000

5.500000

r(-0.495137,-1.594626,0.974494 ) <-3.123195

r(0.495137,-1.594626,0.974494 ) >3.123195

1.410 / 0.980
x=17.594546

y=-2.781153

z=1.699593

-5.716814

-8.559509

5.230811

r(-1.281833,-1.268109,0.774956 ) <-7.228981

r(-0.495137,-1.594626,0.974494 ) >-3.123195

1.410 / 0.980
x=14.966814

y=-5.290067

z=3.232819

-10.874027

-7.281153

4.449593

r(-1.710571,-0.853311,0.521468 ) <-7.622861

r(-1.281833,-1.268109,0.774956 ) >-7.228981

1.410 / 0.980
x=10.874027

y=-7.281153

z=4.449593

-14.966814

-5.290067

3.232819

r(-1.907146,-0.481971,0.294538 ) <-5.45135

r(-1.710571,-0.853311,0.521468 ) >-7.622861

1.410 / 0.980
x=5.716814

y=-8.559509

z=5.230811

-17.594546

-2.781153

1.699593

r(-1.983271,-0.155425,0.094982 ) <-1.953178

r(-1.907146,-0.481971,0.294538 ) >-5.451355

1.410 / 0.980

Table 2: Definition of the 9 cylinders composing the rib at the position Z=0. The four other ribs are just translated to Z= 3 and Z= 6.

 

View Phantom Definition (download as zip, 5k)
phantom syntax explanation

Other Phantoms
Abdomen Head Hip Jaw
Lung Thorax High Contrast Low Contrast