The B0 and B1+ maps required for calculation of the RF pulse of parallel transmission (pTx) are obtained in calibration scans; however, they may be affected by respiratory motion(1). We aimed to compare the reproducibility of B0 and B1+ maps and gradient echo images of the brain scanned with pTx at 7T between free-breathing (FB) and breath-holding (BH) conditions during the calibration scan.Nine healthy volunteers were scanned by 7T MRI using a two-channel quadrature head coil. In the pTx calibration scans performed with FB and BH, the B0 map was obtained from two different TE images and the B1+ map was calculated by the Bloch–Siegert method(2). A gradient-recalled-acquisition in steady state (GRASS) image was also obtained with RF shimming and RF design of pTx, as well as quadrature transmission (qTx). All the scans were repeated over five sessions. The reproducibility of the B0 and B1+ maps and GRASS image was evaluated with region-of-interest measurements using inter-session SD and CV values. Intensity homogeneity of GRASS images was also assessed with in-plane CV.Fig. 1 shows B0 and B1+ maps for five sessions, and their SD maps in one volunteer. The frequency shift was consistent in all scans for both FB and BH; however, the frequency shift in other parts of the brain varied among the five sessions in FB, whereas the variations among five sessions were smaller in BH. These differences in frequency variations between FB and BH were obvious in SD maps, which showed variations among sessions. Fig. 2 shows examples of GRASS images for five sessions in the same volunteer, and the corresponding CV maps. With RF shimming, there were significant changes in the distribution of signals through five sessions in FB, and the CV map showed overall high values. In contrast, those fluctuations were considerably better in BH, and CV maps were similar to qTx. With RF design, significant fluctuations among sessions were also obvious in FB compared to BH, and severely low signals were noted in a number of sessions in FB. The CV map in BH showed lower values than in FB. The high signals in the center of brain were still obvious with qTx and RF shimming in both FB and BH. In contrast, the signal inhomogeneity was not obvious compared with RF design. Inter-session SDs of B0 and B1+ maps of each channel (Fig.3) were significantly smaller in BH (mean, 794.7, 301.5, and 272.8 in FB and 499.5, 155.7, and 163.0 of B0, B1+(Ch0), and B1+(Ch1), respectively. p < 0.01, all). Inter-session CVs of GRASS images (Fig.4) were significantly smaller in qTx(0.023) than BH(0.038) and FB(0.142) (p < 0.01, both); however, the CVs of BH were significantly smaller than that of FB(p < 0.01). In-plane CVs of FB (0.318) and BH(0.309) with RF shimming (Fig.5) were not significantly different with qTx(0.312); however, CVs of FB(0.235) and BH(0.220) with RF design (Fig.5) were significantly smaller than those of qTx(0.310) (p < 0.05 and p < 0.01, respectively)The B0 fluctuation caused by respiration has been actively reported in the field of functional MRI and reported that the phase shifts occurred between inspiration and expiration due to the motion of the chest and local oxygen concentration changes, and this effect became larger in the ultrahigh field(3). And we found also the same phenomenon was seen in B1+ mapping, perhaps because the respiration B0 fluctuations affect the relative frequency shift induced by off-resonance pulses and this might cause the Bloch-Siegert B1+ mapping. Our study revealed BH could reduce the influence of respiratory fluctuations, and had shown higher reproducibility than FB. Our results also showed the variations in GRASS images among sessions were improved by BH, suggesting that reproducibility in B0 and B1+ mapping is important for the reproducibility of GRASS images.BH could improve the reproducibility of B0 and B1+ maps in pTx calibration scans and gradient echo images. These results might facilitate the development of pTx in human brain at 7T.