TimTX array Step 2 - Siemens Healthcare - Siemens AG

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MAGNETOM 7T

TimTX Array Step 2

Answers for life. CAUTION: Investigational Device. Limited by U.S. Federal Law to Investigational Use.

TimTX array Step 2

Integrated pTX Hardware

VB17 TX array software

The TX array system provides 8 RF channels to be operated independently, each driven by its own RF power amplifier (RFPA). The RFPA is designed to be configured for either parallel transmission or for a combined single channel. Key planned features:

The TX array software is based on VB17. Parallel Transmit can be realized on different system levels for specific and general applications. Key planned features: • TX array operation from a single console • Coil-specific default shims for immediate scanning without manual RF shim adjustments • Patient-specific RF shim based on B1 maps (e.g., using the B1 shimming task card) can be applied to any sequence on the scanner for all RF pulses in the sequence • Tailored RF pulses with individual pulse shapes on different channels or dynamically changing RF shims can be programmed on a sequence level • IDEA CD for pTX step 2 including tools to integrate pTX pulses into sequences • Calibration tools to measure e.g., S-parameter matrix

• RF coil interface box for 8/16 TX and 32 RX channels (Figure 2) • Fully integrated cabling up to dedicated on-table pTX coil sockets • Directional couplers pick up the transmitted RF pulse shapes (voltage and phase) automatically for each channel. The RF data are recorded by the MR receiver and are available with the MR raw data • A 32 channel switch-matrix switches the receive paths between RF transmission and MR echo acquisition for recording both RF pulse shapes and MR echoes (Figure 3) • High synchronicity of transmit channels, below 0.5 degree at 300 MHz

Figure 2: New RF coil interface

Figure 3: 32 channel switch matrix

CAUTION: Investigational Device. Limited by U.S. Federal Law to Investigational Use.

2

Inline RF power supervision

Inline local SAR supervision

The new global power supervision is realized by an independent and calibrated system including broadband power meters and a data processing unit (Figure 4). Key planned features:

For the new local SAR supervision, amplitude and phase of the transmitted RF signals are measured with directional couplers (DiCos) located at the rear side of the magnet. The Virtual Observation Point (VOP) concept is implemented for evaluating local SAR inline for the actual multi-channel RF waveform. Key planned features:

• Power meters measure forward and reflected power of each transmit channel continuously at 400 ns sampling intervals and check for unexpected RF transmission

• A VOP generator will be provided, compressing the local electrical fields per unit driving voltage of each channel and the local conductivities for customer built coils (please note: local electrical fields per unit driving voltage of each channel and the local conductivities are provided by the customer) • A [conservative] estimate of local SAR can be calculated inline based on a limited number of VOP matrices and the actual multi-channel RF waveform • Comparison of the observed local SAR values with upper limits across particular time intervals given in the standards can be performed • VOPs will be made available for local SAR optimized pulse design

• Sliding window time averages of the total net power (sum over all transmit channels) will be calculated for time windows of 10 ms, 10 s and 6 min with an update rate of 10 us. User-defined power limits are supervised in order to stop unwanted or excessive RF transmission

For further information on the VOP concept see figure 5 and Eichfelder G, Gebhardt M. in Magn Reson Med. 2011 Nov;66(5):1468-76 and Lee J et al in Magn Reson Med. 2012 Jun;67(6):1566-78)

Figure 4: Multi-channel PALI

Figure 5: Schematics for Virtual Observation Point calculation

CAUTION: Investigational Device. Limited by U.S. Federal Law to Investigational Use.

3

Anatomy specific adjustments

Online pulse design

Two planning suites (Task Cards) will be available for anatomy specific adjustments. Key planned features:

As part of the adjustment planning suites, various options for B1 shimming within the user defined ROIs will be available. Key planned features:

• User configurable protocols for B0 mapping • Relative, quantitative and hybrid B1 mapping techniques • Anatomy specific ROI definition via threshold, simple geometrical forms and arbitrary polygon shapes • Interface for offline adjustment algorithms • Common ROIs for B0 shimming and B1 shimming

• Optimization of a magnitude based cost function – disregarding the excitation phase for improved flip angle homogeneity • Optional optimization of the RF transmit phases only for local high efficiency B1 shimming • Continuous trade-off between excitation efficiency and homogeneity with configurable regularization of the cost function • Configurable cost function for flexible optimization of the excitation flip angle for standard deviation within the ROI, min-max difference or a combination • Visualization of the predicted excitation pattern for quality control

Figure 6: B0 and B1 planning task cards CAUTION: Investigational Device. Limited by U.S. Federal Law to Investigational Use.

4

MAGNETOM 7T TimTX array Step 2 Overview The transmit (TX) array system is an imaging device for research applications, designed for transmission of multiple RF pulses simultaneously through independent RF channels. Varying the spatial distribution of the excitation RF fields over time can allow B1 mitigation or tailored spatial and spectral excitation accelerating multidimensional RF pulses. We have designed the next step in TimTX array technology (step 2) to feature a new RF and SAR supervision and improved workflow and performance functionality. Planned RF and SAR supervision • Multi-channel PALI • Directional couplers for local SAR supervision • 32 channel switch matrix • VOP compression tool Planned workflow and performance • RF coil interface providing plugs for 8 TX channels and associated cabling • VB17A TX array software to operate the system from a single console • B0 and B1 task cards for anatomy specific B0 and B1 shimming • Pre-calibrated TX channels for an automated combined channel operation mode • IDEA CD for pTX step 2 including tools to integrate pTX pulses into sequences A web platform (UHF Community) is available to stay in contact with the pTX developer community at www.mr-idea.com

CAUTION: Investigational Device. Limited by U.S. Federal Law to Investigational Use.

Figure 1: Schematic overview of Step 2 RF supervision

The products mentioned herein are still under development and not commercially available yet. Its future availability cannot be ensured. This research system is not cleared, approved or licensed in any jurisdiction for patient examinations. This research system is not labelled according to applicable medical device law and therefore may only be used for volunteer or patient examinations in the context of clinical studies according to applicable law. On account of certain regional limitations of sales rights and service availability, we cannot guarantee that all products included in this brochure are available through the Siemens sales organization world-wide. Availability and packaging may vary by country and are subject to change without prior notice. Some/All of the features and products described herein may not be available in the United States.

Global Business Unit Siemens AG Healthcare Sector Magnetic Resonance Henkestr. 127 91052 Erlangen Germany Phone: +49 9131 84-0

All devices listed herein may not be licensed according to Canadian Medical Devices Regulations. The information in this document contains general technical descriptions of specifications and options as well as standard and optional features which do not always have to be present in individual cases. Siemens reserves the right to modify the design, packaging, specifications, and options described herein without prior notice. Please contact your local Siemens sales representative for the most current information. Note: Any technical data contained in this document may vary within defined tolerances. Original images always lose a certain amount of detail when reproduced Please find fitting accessories: www.siemens.com/medical-accessories

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