1. A computer readable storage medium having stored thereon a computer program comprising instructions, which, when executed by a computer, cause the computer to:
apply a first plurality of radio frequency (RF) pulses during a first repetition time (TR) interval of a magnetic resonance (MR) pulse sequence to generate a first echo train;
split a plurality of echoes of the first echo train into a plurality of echo pairs;
within a first echo space bounded by an adjacent pair of RF pulses of the first plurality of RF pulses:
apply a first gradient pulse during a first generated echo of a first echo pair;
acquire a first set of k-space data from the first generated echo of the first echo pair and during the application of the first gradient pulse, wherein the first set of k-space data corresponds to a first blade of k-space data;
apply a second gradient pulse after acquisition of the first set of k-space data and during a second generated echo of the first echo pair; and
acquire a second set of k-space data from the second generated echo of the first echo pair and during the application of the second gradient pulse, wherein the second set of k-space data corresponds to a second blade of k-space data in a same k-space as the first set of k-space data, and wherein the second blade has a blade orientation at a different angle than a blade orientation of the first blade; and
reconstruct an image based on the acquired first and second sets of k-space data.
2. The computer readable storage medium of claim 1 wherein the instructions that cause the computer to acquire reconstruct the image cause the computer to reconstruct the image using PROPELLER reconstruction.
3. The computer readable storage medium of claim 1 wherein the instructions further cause the computer to repeat the application of the first and second gradient pulses and the acquisition of the first and second sets of k-space data within additional echo spaces to acquire full first and second blades of k-space data.
4. The computer readable storage medium of claim 3 wherein the instructions further cause the computer to:
apply a rotation matrix prior to a second TR interval of the MR pulse sequence, the rotation matrix configured to rotate acquisition of k-space data;
apply a second plurality of RF pulses during the second TR interval to generate a second echo train;
split echoes of the second echo train into echo pairs;
within respective echo spaces bounded by adjacent pairs of RF pulses of the second plurality of RF pulses:
apply a first gradient pulse during a first generated echo of a respective echo pair;
acquire a third set of k-space data from the first generated echo of the respective echo pair and during the application of the first gradient pulse, wherein the third set of k-space data corresponds to a third blade of k-space data in the same k-space as the first and second sets of k-space data, and wherein the third blade has a blade orientation at a different angle than the first and second blades;
apply a second gradient pulse after acquisition of the third set of k-space data and during a second generated echo of the respective echo pair; and
acquire a fourth set of k-space data from the second generated echo of the respective echo pair and during the application of the second gradient pulse, wherein the fourth set of k-space data corresponds to a fourth blade of k-space data in the same k-space as the third set of k-space data, and wherein the fourth blade has a blade orientation at a different angle than the first, second, and third blades; and
wherein the instructions that cause the computer to reconstruct the image cause the computer to reconstruct the image based on the acquired first, second, third, and fourth sets of k-space data.
5. The computer readable storage medium of claim 3 wherein the instructions further cause the computer to:
apply a first plurality of gradient pulses along a first gradient axis during the first TR, the first plurality of gradient pulses comprising the first gradient pulses;
apply a second plurality of gradient pulses along a second gradient axis during the first TR, the second plurality of gradient pulses comprising the second gradient pulses.
6. The computer readable storage medium of claim 5 wherein the instructions that cause the computer to split the plurality of echoes cause the computer to split the plurality of echoes of the first echo train via application of a plurality of phaser gradients along the first and second gradient axes.
7. The computer readable storage medium of claim 6 wherein an area of the phaser gradients is one half of an area of the first and second gradient pulses.
8. The computer readable storage medium of claim 3 wherein the instructions further cause the computer to apply a pulse scheme prior to the first TR interval, the pulse scheme configured to cause a violation of a Carr-Purcell-Meiboom-Gill (CPMG) condition.
9. The computer readable storage medium of claim 8 wherein the instructions that cause the computer to apply the pulse scheme cause the computer to apply a plurality of pulses according to a diffusion-weighted preparation scheme.
10. The computer readable storage medium of claim 1 wherein the blade orientation of the second blade is perpendicular to the blade orientation of the first blade.
11. A method comprising:
generating an echo train via application of a radio frequency (RF) pulse train during each repetition time (TR) interval of a pulse sequence;
splitting echoes of the echo train into multiple echo pairs, each echo pair comprising a first echo followed by a second echo and occurring during a respective echo space of the RF pulse train;
for each respective echo space:
applying a plurality of gradient pulses toward an imaging object;
during the first echo of the echo pair corresponding to the respective echo space, acquiring magnetic resonance (MR) data for a first k-space blade from the first echo during application of a first pulse of the plurality of gradient pulses; and
during the second echo of the echo pair corresponding to the respective echo space, acquiring MR data for a second k-space blade from the second echo during application of a second pulse of the plurality of gradient pulses, wherein the first and second blades are non-parallel and correspond to a single k-space;
reconstructing the acquired MR data into an image; and
displaying the image to a user.
12. The method of claim 11 wherein the first and second blades are orthogonal.
13. The method of claim 11 wherein splitting comprises:
applying a first phaser gradient along a first gradient axis; and
applying a second phaser gradient along a second gradient axis simultaneously with the first phaser gradient, wherein the second gradient axis is perpendicular to the first gradient axis.
14. The method of claim 13 wherein applying the first and second phaser gradients comprises:
applying the first phaser gradient such that an area thereof is half of an area of the first pulse of the plurality of gradient pulses; and
applying the second phaser gradient such that an area thereof is half of an area of the second pulse of the plurality of gradient pulses.
15. The method of claim 11 further comprising:
applying a first RF pulse of the RF pulse train; and
executing a spin preparation sequence configured to cause a violation of a Carr-Purcell-Meiboom-Gill (CPMG) condition.
16. The method of claim 11 further comprising positioning the imaging object in a bore of an MR system magnet such that a CPMG condition is violated due to eddy current, field inhomogeneity, and susceptibility.
17. The method of claim 11 further comprising rotating acquisition of the first and second k-space blades for each TR interval such that each acquired k-space blade comprises a distinct angular orientation.
18. An MRI apparatus comprising:
a magnetic resonance imaging (MRI) system having a plurality of gradient coils positioned about a bore of a magnet to impress a polarizing magnetic field and an radio frequency (RF) transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly to acquire MR images; and
a computer programmed to:
apply pulses of a pulse sequence toward an imaging object, wherein the pulse sequence comprises a plurality of echo spaces, and wherein the pulses comprise:
a plurality of RF pulses corresponding to the plurality of echo spaces;
a plurality of phaser gradient pulses corresponding to each echo space of the plurality of echo spaces and configured cause a pair of echoes to be generated during each echo space, wherein each pair of echoes comprises a first echo followed by a second echo;
a plurality of readout gradient pulses corresponding to each echo space of the plurality of echo spaces;
acquire k-space data for a first k-space blade during application of a first readout gradient pulse of the plurality of readout gradient pulses in a first echo space and during the first echo of the first echo space;
acquire k-space data for a second k-space blade during application of a second readout gradient pulse of the plurality of readout gradient pulses in the first echo space and during the second echo of the first echo space, wherein the second k-space blade is orthogonal to the first k-space blade, and wherein the first and second k-space blades correspond to a single k-space;
reconstruct acquired k-space data for the first and second k-space blades into an image.
19. The MRI apparatus of claim 18 wherein each phaser gradient pulse of the plurality of phaser gradient pulses has an area corresponding to one half of an area of each readout gradient pulse of the plurality readout of gradient pulses.
20. The MRI apparatus of claim 18 wherein the pulses further comprise a plurality of pulses according to a diffusion-weighted preparation scheme configured to cause a violation of a Carr-Purcell-Meiboom-Gill (CPMG) condition.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A catalyst composition for treating a diesel engine exhaust stream containing a volatile organic fraction comprises a refractory carrier on which is disposed a coating of a catalytic material comprising a catalytically effective amount of ceria having a BET surface area of at least about 10 m2g and a catalytically effective amount of a zeolite.
2. The catalyst composition of claim 1 further including a catalytically effective amount of alumina having a BET surface area of at least about 10 m2g.
3. The catalyst composition of claim 1 wherein the zeolite comprises a three-dimensional zeolite characterized by pore openings whose smallest cross-sectional dimension is at least about five Angstroms and having a silicon to aluminum atomic ratio of greater than 5.
4. The catalyst composition of claim 1 wherein the zeolite comprises Beta zeolite.
5. The catalyst composition of claim 1 wherein the zeolite is selected from the group consisting of Y-zeolite, pentasil, Mordenite, and mixtures thereof.
6. The catalyst composition of claim 3, claim 4 or claim 5 further including a catalytically effective amount of alumina having a BET surface area of at least about 10 m2g.
7. The catalyst composition of claim 2, claim 3 or claim 4 wherein the zeolite comprises from about 10 to 90 percent by weight, the alumina comprises from about 60 to percent by weight, and the ceria comprises from about 60 to 5 percent by weight, of the combined weight of the zeolite, the alumina and the ceria.
8. The catalyst composition of claim 2, claim 3 or claim 4 wherein the zeolite comprises from about 20 to 70 percent by weight, the alumina comprises from about 50 to 20 percent by weight, and the ceria comprises from about 50 to 20 percent by weight, of the combined weight of the zeolite, the alumina and the ceria.
9. The catalyst composition of claim 1, claim 2, claim 3 or claim 4 wherein the zeolite is doped with a catalytic moiety selected from the group consisting of one or more of hydrogen, platinum, rhodium, palladium, ruthenium, osmium, iridium, copper, iron, nickel, chromium and vanadium.
10. The catalyst composition of claim 9 wherein the zeolite is doped with the catalytic moiety by ion-exchanging the zeolite with cationic catalytic moiety.
11. The catalyst composition of claim 9 wherein the catalytic moiety comprises one or both of platinum and iron.
12. The catalyst composition of claim 11 wherein the refractory carrier has a plurality of parallel exhaust flow passages extending therethrough and defined by passage walls on which the catalytic material is coated, and the catalytic moiety comprises platinum and is present in a quantity sufficient to provide from about 5 to 60 gft3 of platinum.
13. The catalyst composition of claim 9 wherein the refractory carrier has a plurality of parallel exhaust flow passages extending therethrough and defined by passage walls on which the catalytic material is coated, and the catalytic moiety comprises from about 2 to 60 gft3 platinum and from about 5 to 50 gft3 iron.
14. The catalyst composition of claim 2, claim 3 or claim 4 wherein the zeolite is disposed in a discrete layer which is overlain by one or more discrete layers containing the alumina and the ceria.
15. The catalyst composition of claim 1, claim 2, claim 3 or claim 4 wherein the refractory carrier has a plurality of parallel exhaust flow passages extending therethrough and defined by passage walls on which the catalytic material is coated, and the ceria and alumina each has a BET surface area of from about 25 m2g to 200 m2g.
16. The catalyst composition of claim 1, claim 2, claim 3 or claim 4 wherein the refractory carrier has a plurality of parallel exhaust flow passages extending therethrough and defined by passage walls on which the catalytic material is coated, and further comprising dispersed platinum carried on the catalytic material in an amount of from about 0.1 to about 60 gft3.
17. The catalyst composition of claim 16 wherein the dispersed platinum is present in the amount of from about 0.1 to 5 gft3.
18. The catalyst composition of claim 15 wherein the refractory carrier has a plurality of parallel exhaust flow passages extending therethrough and defined by passage walls on which the catalytic material is coated, and at least a catalytically effective amount of the dispersed platinum is carried on the ceria.
19. The catalyst composition of claim 1, claim 2, claim 3 or claim 4 wherein the refractory carrier has a plurality of parallel exhaust flow passages extending therethrough and defined by passage walls on which the catalytic material is coated, and further comprising dispersed palladium carried on the catalytic material in a quantity of from about 0.1 to 200 gft3.
20. The catalyst composition of claim 19 wherein the dispersed palladium is present in an amount of from about 20 to 120 gft3.
21. A method for treating a diesel engine exhaust stream containing a volatile organic fraction comprises contacting the stream with a catalyst composition under oxidizing conditions including a temperature high enough to catalyze oxidation of at least some of the volatile organic fraction, the catalyst composition comprising a catalytically effective amount of ceria having a BET surface area of at least about 10 m2g and a catalytically effective amount of a zeolite.
22. The method of claim 21 wherein the catalyst composition further comprises a catalytically effective amount of alumina having a BET surface area of at least about 10 m2g.
23. The method of claim 21 wherein the zeolite comprises a three-dimensional zeolite characterized by pore openings whose smallest cross-sectional dimension is at least about 5 Angstroms and having a silicon to aluminum atomic ratio of greater than 5.
24. The method of claim 21 wherein the zeolite comprises Beta zeolite.
25. The method of claim 21 wherein the zeolite is selected from the group consisting of Y-zeolite, pentasil, Mordenite and mixtures thereof.
26. The method of claim 23, claim 24 or claim 25 further including a catalytically effective amount of alumina having a BET surface area of at least about 10 m2g.
27. The method of claim 26 wherein the zeolite comprises from about 10 to 90 percent by weight, the alumina comprises from about 60 to 5 percent by weight, and the ceria comprises from about 60 to 5 percent by weight, of the combined weight of the zeolite, the alumina and the ceria.
28. The method of claim 21 or claim 22 wherein the zeolite is doped with a catalytic moiety selected from the group consisting of one or more of hydrogen, platinum, rhodium, palladium, ruthenium, osmium, iridium, copper, iron, nickel, chromium and vanadium.
29. The method of claim 28 wherein the zeolite is doped with the catalytic moiety by ion-exchanging the zeolite with a cationic catalytic moiety.
30. The method of claim 28 wherein the catalytic moiety comprises one or both of platinum and iron.
31. The method of claim 21 or claim 22 wherein the refractory carrier has a plurality of parallel exhaust flow passages extending therethrough and defined by passage walls on which the catalytic material is coated, and the catalytic moiety comprises platinum and is present in a quantity sufficient to provide about 5 to 60 gft3 of platinum.
32. The method of claim 22 wherein the zeolite is disposed in a discrete layer which is overlain by one or more discrete layers containing the alumina and the ceria.
33. The method of claim 22 wherein the ceria and the alumina each has a BET surface area of from about 25 m2g to 200 m2g.
34. The method of claim 21 or claim 22 wherein the refractory carrier has a plurality of parallel exhaust stream flow passages extending therethrough and defined by passage walls on which the catalytic material is coated, and the catalyst material further comprises dispersed platinum carried thereon in an amount of from about 0.1 to 60 gft3.
35. The method of claim 34 wherein the dispersed platinum is present in the amount of from about 0.1 to 5 gft3.
36. The method of claim 34 wherein at least a catalytically effective amount of the dispersed platinum is carried on the ceria.
37. The method of claim 21 or claim 22 wherein the temperature of the exhaust stream initially contacted with the catalyst composition is from about 100 C. to 800 C.
38. The method of claim 21 or claim 22 wherein the refractory carrier has a plurality of parallel exhaust stream flow passages extending therethrough and defined by passage walls on which the catalytic material is coated, and the catalytic material further comprises dispersed palladium carried thereon in the amount of from about 0.1 to 200 gft3.