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MultiTransmit solves 3.0T body imaging challenges at the source

White Paper
MRI NetForum Team Philips Healthcare Philips Global

MultiTransmit RF technology enhances image quality by nullifying dielectric shading and speeds up scanning by reducing local SAR. Patient-adaptive MultiTransmit is available on Philips' Achieva 3.0T TX, the first 3.0T system with parallel RF transmission.

Higher field strength paradox

3.0T has rapidly become the preferred field strength for neuro and musculoskeletal MRI because of the higher SNR, spatial resolution and scan speed it offers. However, anyone involved in body and body-related imaging on a 3.0T system has seen the impact of the stronger dielectric effects that may sometimes cause darkened, shaded areas in MR images.

An enabling technology for growing MRI

Philips' MultiTransmit RF technology now addresses these obstacles at their origins. With Achieva 3.0T TX system's MultiTransmit technology, dielectric shading and local SAR challenges have been effectively addressed, for consistent results and enhanced diagnostic confidence. The way is now clear for exceptional 3.0T breast, abdomen, pelvis, spine and heart studies.

MultiTransmit cancels out dielectric effect as soon as it appears

The dielectric effect is non-uniform RF distribution - also called B1 inhomogeneity - caused by changes of the RF wave due to the tissue's properties. The effect is more pronounced at 3.0T than at lower field strengths, as the RF wavelength at 3.0T (about 25 cm), approaches the size of the body. Depending on the size, shape and tissue characteristics of each individual patient, it can result in standing waves.

 

In the Achieva 3.0T X-series, RF-SMART technology reduces SAR and dielectric problems, avoiding the need to use cumbersome dielectric pads. However, only MultiTransmit is able to nullify the dielectric effect before the fact, as it addresses dielectric shading at the source.

 

Conventional imaging using one RF transmission source may create a non-uniform image due to a standing wave. With MultiTransmit, parallel RF sources are tuned so that a standing wave generated by one source is countered by the second source, resulting in images with uniform signal and contrast.

 MultiTransmit: parallel RF transmission from two well-tuned RF sources results
in a uniform signal distribution.
MultiTransmit: parallel RF transmission from two well-tuned RF sources results in a uniform signal distribution.
MultiTransmit: parallel RF transmission from two well-tuned RF sources results in a uniform signal distribution.

MultiTransmit automatically adjusts to each patient's unique anatomy

MultiTransmit creates uniform images by adapting the RF transmission to a patient's size, shape and relative amounts of fat and water. The system automatically optimizes the power, amplitude, phase and waveform of each RF source to tailor the RF transmission to the patient's anatomy. Optimizing RF using parallel RF transmit is also called RF shimming or B1 shimming.

 

Using two completely independent RF sources greatly increases the "degrees of freedom" that the MRI system can use for B1 shimming. Particularly in torso imaging, elimination or signifi cant lessening of dielectric shading with MultiTransmit's patient-adaptive RF technology has resulted in enhanced signal and contrast uniformity and consistent results, patient after patient.

 Conventional single transmit 3T uses only one single RF source, sometimes resulting in dielectric shading, depending on the size, shape and tissue characteristics of the patient. MultiTransmit with multiple RF
sources enable adaption to each patient’s unique anatomy resulting in uniform images.
Conventional single transmit 3T uses only one single RF source, sometimes resulting in dielectric shading, depending on the size, shape and tissue characteristics of the patient. MultiTransmit with multiple RF sources enable adaption to each patient’s unique anatomy resulting in uniform images.
Conventional single transmit 3T uses only one single RF source, sometimes resulting in dielectric shading, depending on the size, shape and tissue characteristics of the patient. MultiTransmit with multiple RF sources enable adaption to each patient's unique anatomy resulting in uniform images.

MultiTransmit reduces local SAR, lifting scan speed limit

With completely independent RF sources, MultiTransmit can also make local SAR distribution more uniform and avoids local high SAR areas, when RF transmit is automatically tailored for each patient. With MultiTransmit hardware (the full chain from RF source via RF transmission to RF reception), it has become possible to optimize RF management, thus better accommodating speed increases in all RF intensive applications.

 

In this way MultiTransmit RF technology has helped clinicians to reduce 3.0T scan times by up to 40%. Alternatively, this gain in speed may be traded for higher resolution at the same scan time.

 Color coding indicates SAR levels in a patient’s body (red is high, blue is low).
MultiTransmit helps to make the local SAR distribution more uniform and the
lowering of localized high SAR enables faster scanning.
Color coding indicates SAR levels in a patient’s body (red is high, blue is low). MultiTransmit helps to make the local SAR distribution more uniform and the lowering of localized high SAR enables faster scanning.
Color coding indicates SAR levels in a patient's body (red is high, blue is low). MultiTransmit helps to make the local SAR distribution more uniform and the lowering of localized high SAR enables faster scanning.

 

Consistent image uniformity for enhanced diagnostic confidence

Conventional 3T image sometimes shows dark areas and brighter spots, but MultiTransmit images consistently provide enhanced uniformity of signal and contrast, patient after patient.

Conventional single transmit MultiTransmit
Conventional single transmit
MultiTransmit
Conventional single transmit MultiTransmit
Conventional single transmit
MultiTransmit
Conventional single transmit MultiTransmit
Conventional single transmit
MultiTransmit

 

Up to 40% faster scanning

MultiTransmit avoids areas of high local SAR, so that up to 40% faster imaging can be achieved. A standard spine examination decreases from 15:07 min. to 9:43 min. with MultiTransmit.

 

Higher resolution in same scan time

The gain in scan speed by preventing high local SAR can be traded to obtain higher spatial resolution in the same scan time.

Conventional        2:52 min. MultiTransmit        Higher resolution, 2:50 min.
Conventional 2:52 min.
MultiTransmit Higher resolution, 2:50 min.


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White Paper
Achieva 3.0T TX
3T, Abdomen, Body, Breast, Liver, Lumbar spine, MultiTransmit, Neuro, Oncology, patient-adaptive, Pelvis, Thoracic spine
 

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