Compressed sensing is a term from the field of digital signal processing. When a signal is digitally sampled, like it happens in an MRI scanner, the signal is not recorded continuously (like old cassette players used to do) but at intervals. A famous theorem from digital signal analysis, the Nyquist theorem, states that for constructing a perfect MR image of 256 x 256 pixels, it is required to sample 256 lines in k-space, each sampled in 256 positions. By doing less, the acquisition will be faster, but the reconstructed image will always be distorted one way or another.
This is exactly what happens with traditional acceleration techniques in MRI, such as halfscan, radial, spiral, increased voxel size and parallel imaging. All of these methods skip parts of k-space during acquisition in order to reduce acquisition time.
However, there will always be a penalty: either a reduced signal-to-noise ratio (halfscan, parallel imaging), lower image resolution (increased voxel size) or image artifacts (spiral, radial).
Compressed sensing is not different, but in practice it is often more forgiving than other acceleration techniques in terms of image distortion and SNR, because it can be designed to primarily sample the MR signals that matter most, while leaving out the rest. A unique aspect about compressed sensing is that it can bypass the aforementioned Nyquist theorem: although not enough samples are taken for perfect image reconstruction, a good compressed sensing reconstruction can successfully remove the inherent artifacts and produce excellent diagnostic images.
Compressed SENSE is the Philips implementation of the compressed sensing principle. It combines dS SENSE, our industry leading parallel imaging method, with compressed sensing. As a result, it can reduce the scan times by up to 50% compared to current examinations without Compressed SENSE.
Philips Compressed SENSE is unique for various reasons:
The Compressed SENSE reconstruction then uses iterative, knowledge-based algorithms to fill in the empty lines in k-space (bottom left). This removes the artifacts while keeping the final image fully consistent with the acquired data (bottom right).
*Compared to Philips MR exams without Compressed SENSE
Our periodic FieldStrength MRI newsletter provides you articles on latest trends and insights, MRI best practices, clinical cases, application tips and more. Subscribe now to receive our free FieldStrength MRI newsletter via e-mail.
Our periodic FieldStrength MRI newsletter provides you articles on latest trends and insights, MRI best practices, clinical cases, application tips and more. Subscribe now to receive our free FieldStrength MRI newsletter via e-mail.
