ontrast-weighted images are commonly acquired in MRI, where one tissue-related parameter usually dominates the contrast, such as T1 or T2 weighting. Relative contrast differences across one image indicate different underlying tissue parameters, but this requires several sequences with different contrast weighting for a final diagnosis. These weighted contrasts provide only qualitative information, which limits the ability of qualitative MRI to depict mostly morphologic abnormalities. Pathologic conditions that alter tissue characteristics on a global or diffuse scale may be missed (1). Instead of indirectly visualizing tissue characteristics by using weighted contrasts, quantitative MRI attempts to directly measure them. Thereby, quantitative MRI could facilitate identification of physiologic changes that do not manifest themselves in morphologic changes or could help detect diffuse tissue changes (eg, in liver [2] and cardiac fibrosis [3]) that remain undetected by using qualitative MRI. It can provide more specific information than does qualitative MRI for characterizing pathologic conditions, such as multiple sclerosis (4) or brain tumors (5). Furthermore, quantitative MRI can be used to assess treatment response (6) or can aid in cases where no side comparison can be performed, such as hippocampal sclerosis (7). With quantitative MRI, diseases can be detected before gross morphologic

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PurposeA 32-channel parallel transmit (pTx) add-on for 7 Tesla whole-body imaging is presented. First results are shown for phantom and in-vivo imaging.MethodsThe add-on system consists of a large number of hardware components, including modulators, amplifiers, SAR supervision, peripheral devices, a control computer, and an integrated 32-channel transmit/receive body array. B1+ maps in a phantom as well as B1+ maps and structural images in large volunteers are acquired to demonstrate the functionality of the system. EM simulations are used to ensure safe operation.ResultsGood agreement between simulation and experiment is shown. Phantom and in-vivo acquisitions show a field of view of up to 50 cm in z-direction. Selective excitation with 100 kHz sampling rate is possible. The add-on system does not affect the quality of the original single-channel system.ConclusionThe presented 32-channel parallel transmit system shows promising performance for ultra-high field whole-body imaging.