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Application tips for prostate imaging

Application Tip
Jones, Alun Philips Healthcare Philips Global

 

Prostate imaging is becoming an increasingly important application for MRI as prostate cancer incidence continues to grow. A report from the United Kingdom indicates that prostate cancer has overtaken lung cancer as the most common form of cancer in males. Frequently, scientific papers are concluding that MRI can provide extremely accurate information for pre-treatment planning, and in most cases now is the modality of choice.

 

In the past, prostate MRI predominantly involved the use of an Endo-cavitary coil, which afforded high signal-to-noise images with small fields-of-views (FOVs) and therefore high resolution images in scan times of 3 to 4 minutes.

 

The disadvantages have been:

  1. Major patient discomfort - leading to patient rejection or motion artifacts in the images.
  2. High SNR close to the coil that rapidly diminishes with distance, resulting in good visualization of structures close to the coil, yet poor or no visualization of structures further from the coil.

 

Anatomical imaging using Endo-cavitary coil (left) and SENSE Cardiac coil (right).

Choose the right coil

Recently, with advances in coil technology and software, the method of choice has involved the use of Synergy phased array surface coils. These coils give images of similar resolution without the disadvantages of the Endo-cavitary coil. It is for the use of these Synergy coils that the following tips are intended.

 

There are two coils ideally suited for prostate imaging: the SENSE Body coil and the SENSE Cardiac coil. Both coils provide good SNR and coverage, but the SENSE Cardiac coil gives up to 20 percent more SNR. From Release 8 on, we recommend using CLEAR (Constant LEvel AppeaRance) to obtain uniform signal intensity across the entire FOV. Other coils can also be used, but will require an increase in scan time to provide the same results as the SENSE Cardiac coil. (See table)

Optimize resolution with flexible matrix

The voxel size is more important than selecting a given FOV or matrix. Using the flexible matrix gives you the ability to obtain the required resolution while achieving the highest SNR possible within a reasonable scan time. If you are using the SENSE Cardiac coil, average scan times per sequence are 4 to 6 minutes.

Choose fold-over direction RL for axial and coronal imaging ...

... to avoid respiratory artifacts in the images.

REST slabs can also be placed over the anterior fat layer of the patient, but this is rarely required if fold-over is set to RL.

Choose fold-over direction FH for sagittal imaging ...

... again to prevent respiratory artifacts from appearing in the images. With both, the RL and FH fold-over directions it is not easy to reduce the RFOV, but because you are using a small FOV (200 to 220 mm), RFOV is not normally used.

Optimize contrast

Prostate imaging is generally performed using T2-weighted sequences. From Release on, it is possible to use DRIVE (Driven Equilibrium) in combination with a multislice technique to increase the T2-weighting of fluids in the image, without increasing scan time.

More applications

Dynamic post-contrast scanning

If dynamic scanning is required, this can be performed using a T1-FFE sequence with ProSet fat suppression. If you have SENSE, the whole prostate can be covered in 3 mm slices and 2 mm in-plane resolution with a temporal resolution of 10 seconds.

Diffusion imaging

The Achieva system is ideally suited for diffusion-weighted imaging of the prostate. Typically, malignant disease will have a reduced ADC value compared to benign disease. The acquisition of high-resolution ADC maps can be achieved with any of the coils mentioned here.

 

 

Left:                                                                 Right:

Dynamic post-contrast scanning                          Patient with tumor: Comparison of Endo-

with the SENSE Cardiac coil                                cavitary coil (top) and SENSE Cardiac coil and

using SENSE Factor 2.                                        diffusion-weighted imaging with b-values

                                                                       0, 125, 250, 375 and 500.



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Application Tip
Achieva 1.5T, Intera 1.5T
Release 1, Release 11, Release 9
Explorer / Nova Dual, Master / Nova, Nova, Nova Dual, Power / Pulsar, Pulsar
Body
 

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