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Effect of Breathhold Position On B0 and B1 in the Kidney

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X Wu

X Wu1*, H Song2 , VA Stenger3 , HM Gach1 , (1) Washington University in St Louis, St Louis, Missouri, (2) The University of Texas MD Anderson Cancer Center, Houston, TX, (3) University of Hawaii at Manoa, Honolulu, HI


SU-K-708-8 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: 708

Purpose: Quantitative magnetic resonance imaging (MRI) in the abdomen is challenging due to the effects of physiological motion, magnetic susceptibility, and magnetic field inhomogeneities (B₀ and B₁). The position of the organs may affect the resulting MRI signal regardless of whether the images are acquired using breathholds, respiratory-gating, or free-breathing. In this study, we examined the effects of three different breathhold positions on B₀ and B₁ measured in the kidney. The objective was to determine the need for signal corrections in quantitative functional (e.g., perfusion) MRI of the kidney when the position of the organs are variable due to free-breathing or variations in the breathhold position.

Methods: Thirteen healthy volunteers (7 males and 6 females) with the mean age of 26 ± 1.5 years received an MRI on a 3T Siemens mMR PET/MRI after informed consent. B₀ and B₁ maps were acquired at three different breathhold positions (deep and shallow inhalation, and full exhalation). Kidney regions were segmented manually in the structural MRI scans and the B₀ and B₁ maps. The segmented B₀ and B₁ maps were co-registered to the segmented structural MRIs. B₀ frequency offsets and B₁ correction factors were generated for the kidneys in each breathhold position. Average B₀ and B₁ values in the kidney regions were calculated and compared across the 13 volunteers.

Results: In each volunteer, the B₀ distribution varied significantly across the kidneys and breathhold positions. Deep inhalation resulted in the highest B₀ variance. B₁ correction offsets were slowly varying. We did not observe large variations in B₁ between the three breathhold positions.

Conclusion: B₁ was slowly varying in the kidney and fairly insensitive to the breathhold position. However, B₀ was sensitive to breathhold position. Suitable signal corrections may be required in quantitative MRI to compensate for B₀ and B₁ variations.

Funding Support, Disclosures, and Conflict of Interest: This research was conducted primarily with the support of National Institutes of Health National Cancer Institute grant R01 CA159471. Our research also received support from the Nevada Cancer Institute, the University of Pittsburgh, and Washington University in St. Louis.

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