How to make this graph in graphviz? - graphviz

Question

My graph:
I could do this by setting the coordinates of each vertex. But I do not know how to set the pixel coordinates.
My attempt to do so:
digraph {
node [shape=circle]
edge [arrowhead=none]
rankdir = BT;
0 -> {1; 2;}
1 -> {3; 4;}
2 -> {4; 8;}
3 -> {9; 5;}
4 -> {5; 10;}
5 -> 11
6 -> {7; 12; 8;}
7 -> {9; 10}
8 -> {10; 14}
9 -> {15; 11}
10 -> {11; 16}
11 -> 17
12 -> {13; 14}
13 -> {15; 16}
14 -> 16
15 -> 17
16 -> 17
0 [pos = "5,0!"]
1 [pos = "4,1!"]
2 [pos = "6,1!"]
3 [pos = "3,2!"]
4 [pos = "5,2!"]
5 [pos = "4,3!"]
6 [pos = "6,3!"]
7 [pos = "4,4!"]
8 [pos = "6,4!"]
9 [pos = "3,5!"]
10 [pos = "5,5!"]
11 [pos = "4,6!"]
12 [pos = "6,6!"]
13 [pos = "4,7!"]
14 [pos = "6,7!"]
15 [pos = "3,8!"]
16 [pos = "5,8!"]
17 [pos = "4,9!"]
}
I renamed the nodes with the letters on the number.
Result:

Answer 1

ex2.dot file:
digraph {
node [ shape=circle, fixedsize=true, width=0.3 ]
edge [ arrowhead=none ]
0 -> {1; 3; 6;}
1 -> {2; 4; 7;}
2 -> {5; 8;}
3 -> {4; 9;}
4 -> {5; 10;}
5 -> 11
6 -> {7; 9; 12;}
7 -> {8; 10; 13;}
8 -> {14; 11;}
9 -> {10; 15;}
10 -> {11; 16;}
11 -> 17
12 -> {13; 15}
13 -> {14; 16}
14 -> 17
15 -> 16
16 -> 17
0 [ pos = "6.00,0.00!" ]
1 [ pos = "5.10,0.30!" ]
2 [ pos = "4.20,0.60!" ]
3 [ pos = "6.60,0.60!" ]
4 [ pos = "5.70,0.90!" ]
5 [ pos = "4.80,1.20!" ]
6 [ pos = "6.30,1.53!" ]
7 [ pos = "5.40,1.83!" ]
8 [ pos = "4.50,2.13!" ]
9 [ pos = "6.90,2.13!" ]
10 [ pos = "6.00,2.43!" ]
11 [ pos = "5.10,2.73!" ]
12 [ pos = "6.60,3.06!" ]
13 [ pos = "5.70,3.36!" ]
14 [ pos = "4.80,3.66!" ]
15 [ pos = "7.20,3.66!" ]
16 [ pos = "6.30,3.96!" ]
17 [ pos = "5.40,4.26!" ]
}
Command:
dot -Kfdp -n -Tpng -o ex2.dot.png ex2.dot
Result: