Implementation of Synthetic MRI into the clinical workflow.

Synthetic MRI is the approach of rapid quantification of MRI parameters and the subsequent synthesis of a whole range of contrast images based on the quantified data. This implies that a single scan is sufficient to generate any conventional T1- or T2 weighted image. It is even possible to visualize far stronger, non-physical contrast such as tissue specific imaging. Application of Synthetic MRI might save up to a third of the patient examination time and will make MRI more reliable and quantitative. The project aims at the clinical implementation of the approach into the PACS system. The technique of rapid quantification is more or less mature but the general use of Synthetic MRI in daily clinic needs to be introduced and validated. In addition to the investigation of the quality of the resulting images the specification of the time-saving aspect will be important. Cardiac Late Enhancement is implemented first and the validation is on-going. Synthetic Brain imaging is implemented at the moment. Future directions will concern the liver.

• Staff:

Janne West		Implemention and developement		CMIV
Erika Peterson		Implementation and developement		CMIV
Anne Aalto		validation on the brain		CMIV/Västervik
Peter Lundberg , Prof		theoretical background quantification		CMIV/Radiophysic
Anne-Marie Landtblom , MD		validation on Multiple Sclerosis		Motala
Jan Engvall , MD		validation on the heart		CMIV/KlinFys
Leif Davidsson , MD		validation on the brain		Radiologi
Örjan Smedby , Prof		validation on the liver		CMIV/Radiologi

• Former Staff:

• Project Description:

Magnetic Resonance Imaging (MRI) is an excellent modality to visualize the human soft tissues. In clinical routine mostly contrast images are acquired. The pixel intensity in these images depends on both patient specific tissue parameters, such as the longitudinal T1 relaxation, the transverse T2 relaxation and the proton density (PD), and on the other hand the MRI scanner settings with parameters such as the echo time (TE), the repetition time (TR), the flip angle () and the application of preparation pulses. The absolute intensity in the images has no direct meaning, it is rather the differences in contrast behavior of the various tissues that leads to a diagnosis. It is therefore required to perform several contrast scans with different scanner settings. This can be a time-consuming and expensive procedure, taking 45 - 60 minutes.

Measuring the absolute MR tissue parameters themselves would result in a more accurate way of characterizing tissue. This would enable the detection of absolute deviation from normal values and assessment of subtle tissue changes over time. However, the required scan time that is associated with the quantification of several MRI parameters has been a major hurdle for the clinical application. In the last few years this hurdle has been lowered dramatically following the development of various methods of rapid MR quantification. Various methods for rapid quantification were demonstrated at the Center of Medical Imaging Science and Visualization in Linköping, Sweden. Simultaneous measurement of T1, T2 and PD of a complete brain can be accurately performed at high resolution in less than 5 minutes or the T1 and PD maps of a whole heart can be captured in a single breath-hold.

Another, less obvious, hurdle for the successful introduction of quantification is the visualization of the absolute MRI data set. Clinicians are not trained in reading these maps and will want to confirm their findings with a conventional set of contrast images. To avoid this redundant scanning the approach of Synthetic MRI can be applied. Using the combination of absolute T1, T2 and PD the expected image intensity can be calculated as a function of MR scanner parameters and hence any conventional T1 or T2 weighted contrast image can be synthesized. This approach will completely alter the way MRI is performed today. A single quantification scan is performed on the patient which results, after the actual examination, in both the absolute maps and an infinite range of contrast images. Moreover, stronger, non-physical contrast images can be shown that are impossible to acquire directly on the scanner, e.g. tissue specific imaging.
Application of Synthetic MRI is expected to significantly decrease the patient examination time and facilitate the diagnostic reading. Data storage and data exchange can be done in a standardized fashion without influence of the specific scanner or software release. For more information see www.syntheticmr.se