1. A method of determining an applicable threshold for determining the critical dimension of at least one category of patterns imaged by atomic force scanning electron microscopy, said method comprising:
from a plurality of patterns, acquiring a pair of images for each pattern, the acquiring comprising
obtaining a first image by an imaging instrumentation implementing an atomic force scanning electron microscopy technique which one seeks to determine the threshold;
obtaining a second image by a reference imaging instrumentation implementing a different technique from said scanning electron microscopy technique;
for each pair of images obtained for each of the patterns:
determining a reference critical dimension via the image obtained by said reference imaging instrumentation;
determining an empirical threshold applicable to the image obtained by said atomic force scanning electron microscopy instrumentation such that said empirical threshold substantially corresponds to said reference critical dimension;
determining a threshold applicable to at least one category of patterns, said threshold being determined from a plurality of empirical thresholds, each empirical threshold corresponding to a pair of images.
2. The method according to claim 1, wherein the threshold is a constant threshold applicable to all pattern categories.
3. The method according to claim 2, wherein the constant threshold is determined by minimizing the difference between the constant threshold and each of the empirical thresholds.
4. The method according to claim 3, wherein the difference between the constant threshold and each of the empirical thresholds is minimized by minimizing the quadratic RMS error.
5. The method according to claim 1, wherein the threshold is a variable threshold according to the category of patterns.
6. The method according to claim 5, wherein the variable threshold is determined by:
calculating an empirical variable threshold for each reference image of a same pattern category, n images being made on m patterns of said same category;
minimizing the difference between the variable threshold and each of the empirical variable thresholds calculated.
7. The method according to claim 6, wherein each empirical variable threshold is a function of the reference critical dimension of the pattern category, of a reference height andor reference angle of said pattern category.
8. The method according to claim 7, wherein said function is a second-degree polynomial.
9. The method according to claim 8, wherein the second-degree polynomial comprises a constant coefficient equal to the constant threshold.
10. The method according to claim 6, wherein the difference between the variable threshold and each of the empirical variable thresholds is minimized by minimizing the quadratic RMS error.
11. The method according to claim 1, wherein the reference imaging instrumentation implements one of the following techniques:
three-dimensional atomic force microscopy, or
Transmission electron microscopy.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for acquiring an image by magnetic resonance comprising:
subjecting an object to be imaged to a constant and uniform magnetic field;
exciting a part of the object by a series of sequences of P electromagnetic RF excitations in the presence of field gradient pulses;
effecting a progressive variation, during a first sequence, of the value of a pulse of a phase-encoding gradient by a given step value between a negative value equal to n times this step value and a positive value equal to N times this step value;
during another sequence following the first sequence, the negative value of a pulse of the phase-encoding gradient is made to vary n+m times by the same given step value; and
acquiring a signal usefully only in response to the n last negative pulses and the N positive pulses of the phase-encoding gradient.
2. The method according to claim 1 wherein
after the n+N electromagnetic signals acquired in each sequence, a number of positive pulses of the phase-encoding gradient equal to P\u2212(n+m+N) is applied.
3. The method according to claim 1 wherein
a first series of sequences is performed in correspondence with a selection of a first slice in the part of the object to be imaged;
a second series of sequences is performed in correspondence with a selection of a second slice in the part of the object to be imaged; and
the sequences of the first series being made interlaced with the sequences of the second series.
4. The method according to claim 2 wherein
a first series of sequences is performed in correspondence with a selection of a first slice in the part of the object to be imaged;
a second series of sequences is performed in correspondence with a selection of a second slice in the part of the object to be imaged; and
the sequences of the first series being made interlaced with the sequences of the second series.
5. The method according to claim 3 wherein
four series of sequences are acquired in correspondence with selections of four slices in the part of the object to be imaged, that are preferably contiguous; and
the sequences of all the series being made in a state of mutual interlacing.
6. The method according to claim 4 wherein
four series of sequences are acquired in correspondence with selections of four slices in the part of the object to be imaged, that are preferably contiguous; and
the sequences of all the series being made in a state of mutual interlacing.
7. The method according to claim 1 wherein
the durations of the n+m echoes correspond to different values of an effective echo time corresponding to the spin-spin relaxation constant of atoms of the object to be imaged; and
from one sequence to another, the durations of the n+m echoes develop from a low value to a high value of this echo time or vice versa.
8. The method according to claim 2 wherein
the durations of the n+m echoes correspond to different values of an effective echo time corresponding to the spin-spin relaxation constant of atoms of the object to be imaged; and
from one sequence to another, the durations of the n+m echoes develop from a low value to a high value of this echo time or vice versa.
9. The method according to claim 3 wherein
the durations of the n+m echoes correspond to different values of an effective echo time corresponding to the spin-spin relaxation constant of atoms of the object to be imaged; and
from one sequence to another, the durations of the n+m echoes develop from a low value to a high value of this echo time or vice versa.
10. The method according to claim 4 wherein
the durations of the n+m echoes correspond to different values of an effective echo time corresponding to the spin-spin relaxation constant of atoms of the object to be imaged; and
from one sequence to another, the durations of the n+m echoes develop from a low value to a high value of this echo time or vice versa.
11. The method according to claim 5 wherein
the durations of the n+m echoes correspond to different values of an effective echo time corresponding to the spin-spin relaxation constant of atoms of the object to be imaged; and
from one sequence to another, the durations of the n+m echoes develop from a low value to a high value of this echo time or vice versa.
12. The method according to claim 6 wherein
the durations of the n+m echoes correspond to different values of an effective echo time corresponding to the spin-spin relaxation constant of atoms of the object to be imaged; and
from one sequence to another, the durations of the n+m echoes develop from a low value to a high value of this echo time or vice versa.
13. The method according to claim 7 wherein
the low value is equal to about 30 milliseconds and the high value is equal to about 90 milliseconds.
14. The method according to claim 8 wherein
the low value is equal to about 30 milliseconds and the high value is equal to about 90 milliseconds.
15. The method according to claim 9 wherein
the low value is equal to about 30 milliseconds and the high value is equal to about 90 milliseconds.
16. The method according to claim 10 wherein
the low value is equal to about 30 milliseconds and the high value is equal to about 90 milliseconds.
17. The method according to claim 11 wherein
the low value is equal to about 30 milliseconds and the high value is equal to about 90 milliseconds.
18. The method according to claim 12 wherein
the low value is equal to about 30 milliseconds and the high value is equal to about 90 milliseconds.
19. The method according to claim 1 wherein
the sequences are performed during a same holding of the breath of a patient whose body is being examined.
20. The method according to claim 2 wherein
the sequences are performed during a same holding of the breath of a patient whose body is being examined.
21. The method according to claim 3 wherein
the sequences are performed during a same holding of the breath of a patient whose body is being examined.
22. The method according to claim 5 wherein
the sequences are performed during a same holding of the breath of a patient whose body is being examined.
23. The method according to claim 7 wherein
the sequences are performed during a same holding of the breath of a patient whose body is being examined.
24. The method according to claim 13 wherein
the sequences are performed during a same holding of the breath of a patient whose body is being examined.
25. The method according to claim 1 wherein
the part of the object examined is a patient’s heart;
the sequences are all synchronized with a heartbeat of the patient; and
the patient is brought to hold his breath for the totalized duration of all the sequences of the series of sequences.
26. The method according to claim 2 wherein
the part of the object examined is a patient’s heart;
the sequences are all synchronized with a heartbeat of the patient; and
the patient is brought to hold his breath for the totalized duration of all the sequences of the series of sequences.
27. The method according to claim 3 wherein
the part of the object examined is a patient’s heart;
the sequences are all synchronized with a heartbeat of the patient; and
the patient is brought to hold his breath for the totalized duration of all the sequences of the series of sequences.
28. The method according to claim 5 wherein
the part of the object examined is a patient’s heart;
the sequences are all synchronized with a heartbeat of the patient; and
the patient is brought to hold his breath for the totalized duration of all the sequences of the series of sequences.
29. The method according to claim 7 wherein
the part of the object examined is a patient’s heart;
the sequences are all synchronized with a heartbeat of the patient; and
the patient is brought to hold his breath for the totalized duration of all the sequences of the series of sequences.
30. The method according to claim 13 wherein
the part of the object examined is a patient’s heart;
the sequences are all synchronized with a heartbeat of the patient; and
the patient is brought to hold his breath for the totalized duration of all the sequences of the series of sequences.
31. The method according to claim 19 wherein
the part of the object examined is a patient’s heart;
the sequences are all synchronized with a heartbeat of the patient; and
the patient is brought to hold his breath for the totalized duration of all the sequences of the series of sequences.
32. The method according to claim 25 wherein
the holding of the patient’s breath is preceded by a set of sequences of P electromagnetic RF excitations.
33. The method according to claim 26 wherein
the holding of the patient’s breath is preceded by a set of sequences of P electromagnetic RF excitations.
34. The method according to claim 27 wherein
the holding of the patient’s breath is preceded by a set of sequences of P electromagnetic RF excitations.
35. The method according to claim 28 wherein
the holding of the patient’s breath is preceded by a set of sequences of P electromagnetic RF excitations.
36. The method according to claim 29 wherein
the holding of the patient’s breath is preceded by a set of sequences of P electromagnetic RF excitations.
37. The method according to claim 30 wherein
the holding of the patient’s breath is preceded by a set of sequences of P electromagnetic RF excitations.
38. The method according to claim 31 wherein
the holding of the patient’s breath is preceded by a set of sequences of P electromagnetic RF excitations.
39. The method according to claim 1 wherein N is greater than n.
40. The method according to claim 2 wherein N is greater than n.
41. The method according to claim 3 wherein N is greater than n.
42. The method according to claim 5 wherein N is greater than n.
43. The method according to claim 7 wherein N is greater than n.
44. The method according to claim 13 wherein N is greater than n.
45. The method according to claim 19 wherein N is greater than n.
46. The method according to claim 25 wherein N is greater than n.
47. The method according to claim 32 wherein N is greater than n.
48. An apparatus for acquiring an image by magnetic resonance comprising:
means for subjecting an object to be imaged to a constant and uniform magnetic field;
means for exciting a part of the object by a series of sequences of RF excitations;
means for applying a series of magnetic field gradient pulses to the object;
means for effecting a progressive variation, during a first sequence, of a value of a pulse of a phase-encoding gradient by a given step value having a negative value equal to n times this step value; and
means for effecting a progressive variation, during the first sequence, of a value of a pulse-encoding gradient by a step value having a positive value equal to N times the step value;
means for varying the negative value of the pulse-encoding gradient during another sequence following the first sequence, n+m times by the same given step value; and
means for acquiring a signal usefully only in response to the n last negative pulses and the N positive pulses of the phase-encoding gradient.
49. The apparatus according to claim 48 comprising:
means for acquiring after the n+N electromagnetic signals in each sequence, a number of positive pulses of the phase-encoding gradient equal to P – (n+m+N) is applied.
50. The apparatus according to claim 48 comprising:
means for performing a first series of sequences in correspondence with a selection of a first slice in the part of the object to be imaged;
means for performing a second series of sequences in correspondence with a selection of a second slice in the part of the object to be imaged; and
means for interlacing the sequences of the first series with the sequences of the second series.
51. The apparatus according to claim 50 comprising:
means for acquiring four series of sequences in correspondence with selections of four slices in the part of the object to be imaged, that are preferably contiguous; and
means for providing a state of mutual interlacing the sequences of all the series.
52. The apparatus according to claim 48 comprising:
means for causing the durations of the n+m echoes to correspond to different values of an effective echo time corresponding to the spin-spin relaxation constant of atoms of the object to be imaged; and
means for causing from one sequence to another, the durations of the n+m echoes develop from a low value to a high value of this echo time or vice versa.
53. The apparatus according to claim 52 wherein
the low value is equal to about 30 milliseconds and the high value is equal to about 90 milliseconds.
54. The apparatus according to claim 48 comprising:
means for performing the sequences during a same holding of the breath of a patient whose body is being examined.
55. The apparatus according to claim 48 wherein:
the part of the object examined is a patient’s heart;
means for synchronizing all the sequences with a heartbeat of the patient; and
the patient is brought to hold his breath for the totalized duration of all the sequences of the series of sequences.
56. The apparatus according to claim 55 wherein
the holding of the patient’s breath is preceded by a set of sequences of P electromagnetic RF excitations.
56. The apparatus according to claim 48 wherein N is greater than n.
57. A computer program product comprising a computer useable medium having computer readable program code means embodied in the medium, the computer readable program code. means implementing the method according to claim 1.
58. An article of manufacture for use with a computer system, the article of manufacture comprising a computer readable medium having computer readable program code means embodied in the medium, the program code means implementing of the method according to claim 1.
59. A program storage device readable by a machine tangibly embodying a program of instructions executable by the machine to perform the method according to claim 1.