3D-Fast Spin

Inspection Of Magnetic Resonance Cholangiopancreatography ( MRCP) with Technique 3D-Fast Spin of Echo Base On SENSE ( Sensitivity Encoding) [at] MRI 1,5 T*
Inspection Of MRCP ( Magnetic Resonance Cholangiopancreatography) is image technique of non-invasif in the MRI ( Magnetic Resonance Imaging ) used to evaluate gall bladder tissue, pancreas with the network which in this time was often used in radiography . Technique of MRCP resulting the image with characteristic of T2 Weighted ( T2-W) where the aqueous dominant tissue higher than background tissue. To reach this image like this, the technique of MRI which was often used in MRCP is 3D-Fast Spin of Echo. This Technique need longer time than technique 2D-FSE so that need special technical strategy. So with Parallel Imaging or iPAT ( Parallel Acquisition Technology integrated), hence problems of time of Acquisition in 3D-FSE can be solved. With bases of SENSE (Sensitivity Encoding) hence process inspection of MRCP with technique 3D-FSE 1,5 T intensity, imaging with high quality.
Like other soft tissue image technique, In the inspection of MRCP ( Magnetic Resonance Cholangiopancreatography) that is inspection of gall bladder tissue, pancreas and their network needed by image character of T2-W where vision of signal in aqueous dominant tissue more bright than network considering fat. To resulting this image of T2-Weighted, So the imaging technique which was often used is technique of Fast Spin Echo ( FSE) or Turbo Spin of Echo ( TSE) where time of TR and TE taken length. This technique is first generation [of] image technique quickly ( Fast Imaging Technique) formulated by jürgen Hennig in the year 1986. This technique have excellence compared to technique Spin Echo conventional, that is time of akuisisi quicker and yield image with high resolution till matrix 512 x 512 . Besides from a study show usage of price of ETS (Echo Train Spacing) long [about/around] 12-15 ms [at] technique 3D-FSE yielding compared to higher level contrast [of] price of ETS the shortness [at] MRCP.
3D Fast Spin
Echo Technique use pulse RF 1800 more one after RF pulse 90 so called as ETL ( Echo Train Length)] or RARE Factor/Turbo Factor. Amount of this ETL also show the amount formed echo signal in each time of TR. Amount of ETL can even (General Electric) or anomalous (of Siemens) with amount usually between 3-32. But in some marks of MRI the amount of ETL in techniques of FSE can reach 256.
Now, development of technique Fast Spin Echo has enabled to apply technique of acquisition 3D-FSE. This technique useful in much technique like brain image applications, spinals cervical, spinals lumbar where image with character T2-W needed more than one plane. Elementary idea of image 3D is encoding phase gradient do not only residing in direction of y but also in z direction like showed [at] picture 2B. Equally slices multiple in technique 2D-FSE changed with slab multiple in 3D-FSE.
Gradien with high activity show make reduction of gradient duration so that enable to be applying the price of ETL to higher level and reduction of TE . With existence of Ny and of Nz in direction of gradient Phase Encoding axis of the ordinate and z ,so time of acquisition 3D-FSE expressed :
T(3D-Fse )= ( TR X NEX Ny Nz) x x / etl ( 1)
Description : TR = Time Repetition
( NEX ms) = amount of Ny acquisition = Amount of Phase encoding at directions of y
Nz = Amount of Phase encoding [at] z directions of ETL = Echo Train Length
In general technique 3D-FSE besides owning excellence as follows

1. Result compared to higher level SNR 2D-FSE with equation: SNR (3D) = V Nz. SNR ( 2D) ( 2)
2. Owning high isotropic resolution (A x =A y = A z)
3. Result smaller volume partial because flimsier slice
4. Can result reform in various direction (Rectangular FOV).

SENSE

Problems of time of acquisition image data in MRI not only overcome with speed of Gradient encoding system. At 1999 have been developed the technology is known as SENSE ( Sensitivity Encoding). This Technique is developed by Pruessmann and friend, in Institute Technique of Biomedical ETH Zurich, Swiss. Basic Idea of SENSE is to heighten speed of image acquisition without modify work of gradient, but in the receiver of RF coils systems. In this time, application of SENSE system has been exploited for the image of imaging cine cardiac, fMRI and MR Spectroscopy. With existence of SENSE hence work system reconstruct technique 3D-FSE, especially in the case of time of acquisition image can be improved. By using multiple coil receiver hence process to image reconstruct of MRI can be done parallels.
With SENSE strategy of image reconstruct done with reduction of amount of Phase encoding with factor called R ( SENSE Factor) that resulting reduction of FOV accompanied by the happening of aliasing. With conventional MRI by one coil receiver of image aliasing is irreversible, so that k-space under sampling cannot use. By using technique of acquisition coil multiple, at this SENSE constraint can overcome. Mechanism of SENSE is contribution of encoding from sensitivities coil. Knowing the sensitivities coil hence process return to image reconstruct image that aliasing progress can be calculated with Linear Algebra algorithm.
Biggest Technical SENSE problem is the SNR ( Signal To Noise Ratio). Link geometric between not ideal coil make of noise in image. This effect is expressed with local geometric factor g which the was price of less him is equal to one. Mathematically link of SNR in SENSE expressed;
Rg SNR sense =SNR conventional/gVr
Theoretically , reconstruct SENSE work with factor reduce R as according to amount of receiver related used coils g so usage of R factor only equal to 3-4 in 6 coil receiver.
Audit Technic of MRCP :

1. Patient suggested to fast 8 hour before inspection
2. Install coil body and censor of patient respiratory
3. Select to set menu 3D MRCP in computer
4. Doing planning of pre scan of axial, and sagital and coronal plane
5. Reference scan to calibrate technique coil receiver sensitivities of SENSE. at the same time give instruction hold breath to patient
6. At the (time) of acquisition work to change the parameter of acquisition
7. Run Abdomen protocol
8. Run planning in cutting of axial abdomen in area of heparin, bladder gland then scanning each area with running 3D MRCP
9. Now we got 3D MRCP data image.
10. Doing post-processing as according to requirement.

RESULT OF
By using parameter of acquisition which is on above table hence by using MRI 1,5 T obtained by results reconstruct:

Image 1. Man ( 71 year) with parameter of acquisition TR : 1139 ms, TE: 600 ms, NEX 1 , Matrix : 256, FOV 280 mm, RFOV: 91%, Nz : 100, THK: 2 / 1 mm, ETL : 120, Factor SENSE : 2, time of acquisition : 1 minute 45 second.

Image 2. Man ( 13 year) with parameter of acquisition TR : 1090 ms, TE: 600 ms, NEX 2 , Matrix : 256, FOV 280 mm, RFOV: 64%, Nz : 80, THK: 2 / 1 mm, ETL : 85, Factor SENSE : 2, time of acquisition: 2 minute 39 second.







Image 3.. Man ( 43 year) with parameter of acquisition TR : 1139 ms, TE: 600 ms, NEX 2 , Matrix : 256, FOV 280 mm, RFOV: 91%, Nz : 120, THK: 2 / 1 mm, ETL : 120, Factor SENSE : 2, time of acquisition: 4 minute 8 second.







Image 4.. Woman ( 23 year) with parameter of acquisition TR : 1135 ms, TE: 600 ms, NEX 2 , Matrix : 256, FOV 280 mm, RFOV: 91%, Nz : 120, THK: 2 / 1 mm, ETL : 119, Factor SENSE : 2, time of acquisition : 4 minute 7.