Segment-resolved assessment of hydration effects on liver water-specific T1 in comparison with T1-MOLLI and transient elastography

Introduction

Liver biopsy remains the reference standard for characterizing diffuse liver disease, but its invasiveness, sampling variability, and limited suitability for longitudinal monitoring continue to drive interest in quantitative magnetic resonance imaging (MRI) biomarkers (1). T1 mapping is a promising technique for evaluating parenchymal changes. Hepatic T1 increases with fibrosis (2), which is associated with the expansion of the extracellular matrix, and may be further prolonged in the presence of inflammation and edema, reflecting increases in extracellular water content and altered tissue microstructure (3-5). Recent studies have demonstrated that hepatic T1 mapping has diagnostic performance comparable to that of established noninvasive approaches for assessing liver fibrosis and inflammation (6).

However, native T1 is biased by hepatic fat, iron, and transmit radiofrequency field (B₁⁺) inhomogeneity, among other factors, limiting reproducibility and interpretation, particularly in populations with steatosis or iron overload (7,8). Water-specific T1 (wT1) mapping reduces fat-related bias by isolating the water signal and has shown improved performance for fibrosis staging and inflammatory assessment (6,9-12). Reference liver wT1 values at 3-T are now available, enabling differentiation between healthy and pathological populations (13).

While technical advances have improved the characterization of liver wT1 in the presence of other confounding factors, such as iron, wT1 interpretability is compromised by insufficiently characterized hydration-related variability. Hydration is a relevant and dynamic physiological factor that alters extracellular water content and perfusion. Prior studies reported increases in hepatic T1 following changes in hydration or glycogen loading (14) and in wT1 after isotonic drink intake (15). However, these investigations relied on single-slice shMOLLI imaging, limiting the ability to assess segmental variation. Given known regional differences in hepatic perfusion and microstructure, it remains unclear whether hydration affects all liver segments uniformly.

A broad liver assessment is necessary to characterize physiological wT1 variability throughout the organ. Conventional multi-slice and three-dimensional T1 mapping techniques offer broader spatial coverage but may be limited by B₁⁺ sensitivity or prolonged acquisition times (11). A recently proposed continuous inversion-recovery Look-Locker (CIR-LL) method enables multi-slice wT1 mapping across all Couinaud segments within an 11-second breath-hold using water-fat separation and dictionary matching (16). This approach is robust to B1⁺ inhomogeneities and allows practical whole-liver characterization within a clinically feasible acquisition time, supporting patient compliance.

In summary, the characterization of the hydration effect on wT1 across the liver has not been addressed. In this study, we evaluate the impact of hydration on wT1 across all liver segments using the accelerated multi-slice CIR-LL wT1 mapping method. For comparison, we assess hydration-related changes in liver stiffness measured by vibration-controlled transient elastography (VCTE) and in single-slice T1-modified Look-Locker inversion recovery (T1-MOLLI) measurements.

Methods

Study cohort

A total of 29 healthy volunteers (16 males, 13 females; mean age 25±7 years) were prospectively recruited. Eligibility criteria included the absence of known liver disease or prior abdominal surgery, normal baseline liver laboratory values, and no contraindications to MRI.

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Ethics Committee of the Technical University of Munich (TUM) (No. 2024-550-S-SB) and informed consent was taken from all individual participants.

Study protocol

Each participant completed two standardized sessions. The volunteers underwent blood sampling to monitor their health status, VCTE to assess liver stiffness, and an MRI examination, all of which are described in the sections below. The first session was performed after a ≥8-hour fast, with no fluid or food intake. The second session took place after ingestion of 1 L of water, followed by a standardized equilibration period of 1 hour to ensure a consistent hydration state. Both sessions were conducted on the same day under identical technical conditions.

Clinical measurements

Laboratory testing was performed on the day of examination, immediately before the MRI acquisition and VCTE assessment, to confirm normal liver function and the absence of clinically relevant systemic abnormalities. Detailed laboratory results are provided in Table S1.

MRI acquisition

All imaging was performed on a 3-T MRI system (Ingenia Elition X; Philips Healthcare, Best, the Netherlands). Standard liver imaging included axial T2-weighted imaging and quantitative mDixon proton density fat fraction (PDFF) and T2* mapping for whole-liver assessment.

wT1 mapping was performed using a CIR-LL sequence with interleaved-echo-time (TE) single-shot spiral readout, combined with water-fat separation and dictionary matching (16). The CIR-LL sequence starts with a slice-selective adiabatic inversion pulse followed by a low-flip-angle RF pulse train [repetition time (TR) =12 ms; TE1/TE2 =2.3/3.3 ms; flip angle =5°]. One hundred interleaved echo spiral images were acquired per slice (spiral readout time =5.6 ms, acceleration factor R=15, acquisition time =1.2 s per slice). Water-fat separation was achieved using the interleaved-TE images and an adipose tissue seven-peak fat model (17) while wT1 values were estimated by dictionary-based (T1 range 100–3,000 ms) fitting of the water-only signal evolution. This CIR-LL method has been shown to be repeatable and robust to B₁⁺ inhomogeneities. The signal model assumes ideal adiabatic inversion behavior. The inversion profile was evaluated experimentally, confirming negligible cross-talk effects for the selected acquisition parameters. Magnetization transfer effects are not explicitly incorporated into the signal model. In addition, T2* effects were neglected due to the short time between the consecutive two TEs.

Nine liver slices were acquired in an interleaved manner (slice 1, 4, 7, 2, 5, 8, 3, 6, 9) with the wT1 mapping method in a single 11-s breath-hold covering all Couinaud segments. For comparison, a modified Look-Locker inversion recovery (T1-MOLLI) acquisition was performed for T1 mapping on a single slice at the level of the portal vein bifurcation using matched in-plane resolution. Thus, the T1-MOLLI map captures S1 and the junctions between liver segments: S2/3, S4a/b, S5/8, and S6/7.

The sequence parameters are provided in Table S2.

Liver stiffness measurement (LSM) by transient elastography

LSMs were obtained using transient elastography on a VCTE system equipped with a 3.5 MHz ultrasound transducer (FibroScan, M-probe, Echosens, Paris, France) (18). LSM was acquired in the right hepatic lobe, targeting a region of at least 6 cm parenchymal thickness and free of major vascular structures or proximity to the gallbladder, to minimize technical artifacts. For each volunteer, a minimum of 10 valid measurements with a success rate above 60% was required for the acquisition to be considered reliable, in line with established quality criteria (19). Liver stiffness values are reported in kilopascals (kPa). The median of all validated measurements (provided by the system) was used as the representative LSM for further analysis. Reliable TE was defined as IQR/median ≤30% with ≥10 valid measurements (20).

Region of interest (ROI) definition

ROI placement for the entire cohort was performed by a physician in training with 5 years of experience. All ROIs were reviewed by a radiologist with 4 years of experience. A subset of 15 cases was evaluated by a board-certified radiologist with 6 years of experience. ROI placement was performed on a PACS workstation (Sectra AB, Linköping, Sweden). For each volunteer, circular ROIs (15 mm diameter) were defined in each Couinaud segment (S1–8) on the PDFF, T2*, and wT1 maps. For the T1-MOLLI map, 5 ROIs were placed: S1, S2/3, S4a/b, S5/8, and S6/7. ROIs were defined independently on each map before and after hydration, using T2-weighted images as an anatomical reference.

Data analysis

Inter-reader reproducibility was assessed by comparing ROI measurements of the 15 cases analyzed by both readers using the intraclass correlation coefficient (ICC; [2,1], two-way random-effects model, absolute agreement). The ICC calculation was performed using all ROI values (before and after hydration) for T2*, PDFF, T1-MOLLI, and wT1.

The measurements of both hydration states were analyzed and compared to characterize the hydration effect. For the entire cohort, descriptive statistics for PDFF, T2*, T1-MOLLI, and wT1 were estimated for both hydration states, including mean, standard deviation (SD), and range. Paired two-sided t-tests, with statistical significance defined as P<0.05, were performed using subject-level mean values across liver segments to compare PDFF, T2*, T1-MOLLI and wT1 measurements before and after hydration. Associations among liver stiffness (VCTE), wT1, and T1-MOLLI were assessed across hydration states using linear regression and Pearson correlation coefficients in the entire cohort. The same methods and Bland-Altman plots were used to assess agreement in the mean per participant between wT1 and T1-MOLLI at both hydration states. Segment-level wT1 and T1-MOLLI values were summarized across the cohort. To assess hydration effects at the segment level, paired wT1 and T1-MOLLI measurements from all participants were pooled per liver segment and compared between the fasting and post-hydration sessions. In addition, paired two-sided t-tests, with statistical significance defined as P<0.05, were performed for each liver segment and the resulting P values were adjusted for multiple testing using the Benjamini-Hochberg false discovery rate (FDR) procedure.

In addition, spatial heterogeneity due to segmental variation within subjects was explored. For this, wT1 and T1-MOLLI values were evaluated across all liver segments for each participant.

To quantify within-subject segmental heterogeneity, the SD and coefficient of variation (CV) of segmental wT1 were calculated for each subject. Group values are reported as mean ± SD across subjects. Differences in these heterogeneity metrics before and after hydration were assessed at the subject level using paired two-sided t-tests, with statistical significance defined as P<0.05. To further illustrate both the hydration effect and spatial heterogeneity, wT1 values across the Couinaud segments were compared between hydration states within each subject.

Results

Study cohort

Twenty-nine healthy volunteers completed both imaging sessions. All baseline laboratory values and VCTE measurements (Table S1) were within reference ranges, confirming the absence of liver disease or systemic abnormalities.

Image quality and coverage

The accelerated wT1 sequence produced high-quality maps with complete coverage of all Couinaud segments across nine slices for each volunteer (Figure 1A). In contrast, the T1-MOLLI acquisition was limited to a single slice at the level of the portal vein bifurcation, capturing only segmental junctions and the caudate lobe (Figure 1B).

Figure 1 Liver coverage. (A) nine-slice wT1 maps of a volunteer obtained in an 11-s breath-hold demonstrating full coverage of all Couinaud segments. (B) Single-slice T1-MOLLI map corresponding to the marked slice (magenta) in the wT1 maps. The T1-MOLLI map was planned at the level of the portal vein bifurcation, depicting only the junctions between liver segments. T1-MOLLI, T1-modified Look-Locker inversion recovery; wT1, water-specific T1.

Inter-reader reproducibility

Inter-reader reproducibility was high for all quantitative MRI parameters. ICC [2, 1] values were 0.99 for T2*, 0.99 for PDFF, 0.88 for T1-MOLLI and 0.98 for wT1, each with narrow 95% confidence intervals (Figure S1).

Global hydration-induced changes

The statistics for the entire cohort show minimal changes in PDFF and T2*, and an increase in T1-MOLLI and wT1 due to hydration (Table 1). Following ingestion of 1 L of water, wT1 increased (26.9 ms), with the magnitude of change exceeding that observed for T1-MOLLI (8.6 ms). Furthermore, subject-level paired comparisons between hydration states showed significant differences for PDFF (P=0.042), T2* (P=0.003) and wT1 (P<0.001), whereas T1-MOLLI did not show a significant change (P=0.320). Representative T2-weighted and multi-parametric images, including PDFF, T2*, T1-MOLLI, and wT1 maps, are shown for both hydration states in Figure 2. The wT1 maps demonstrated clear anatomical delineation, representative of the multi-slice coverage provided by the method, whereas the T1-MOLLI maps reflected the expected single-slice geometry. PDFF and T2* maps did not show visually apparent differences between fasting and hydrated conditions.

Figure 2 Representative images of a volunteer. Example case with T2-weighted, PDFF, T2*, T1-MOLLI, and wT1 maps before and after hydration. S4 ROI values (white circles) and their mean value (dark boxes) are shown in all maps depicting hydration-induced T1-MOLLI (89 ms) and wT1 (91 ms) changes. PDFF, proton density fat fraction; ROI, region of interest; T1-MOLLI, T1-modified Look-Locker inversion recovery; wT1, water-specific T1.

Hydration-induced changes in liver stiffness, T1-MOLLI, and wT1

LSMs obtained by VCTE showed a consistent physiological range across participants, with no indication of underlying pathology. While liver stiffness, T1-MOLLI, and wT1 measurements all demonstrated positive correlations between the fasting and hydrated states, T1-MOLLI exhibited the greatest hydration-related variability, reflected in a lower Pearson r (Figure 3). The regression slope for wT1 between sessions was closer to unity and more similar to that observed for liver stiffness than that of T1-MOLLI. Moreover, the wT1 correlation between fasting and hydrated measurements was stronger (r=0.89) than that observed for liver stiffness (r=0.63) and T1-MOLLI (r=0.71).

Figure 3 Liver stiffness, T1-MOLLI, and wT1 variation due to hydration. Linear regression and correlation between before and after hydration states of (A) the liver stiffness measurements obtained with the VCTE, a point representing a volunteer, (B) T1-MOLLI showing the measurements in S1, S2/3, S4a/b, S5/8, and S6/7 for all volunteers, and (C) wT1 considering all Couinaud segments for all volunteers. T1-MOLLI, T1-modified Look-Locker inversion recovery; VCTE, vibration-controlled transient elastography; wT1, water-specific T1.

Agreement between wT1 and T1-MOLLI, and segmental effects

While the mean wT1 and T1-MOLLI values per participant showed a positive correlation in both hydration states (Figure 4A), after hydration measurements correlated more strongly (Pearson r=0.78) than before hydration (Pearson r=0.64). Bland-Altman analysis revealed that T1-MOLLI consistently overestimated wT1, with positive mean biases of 82.7 ms under fasting conditions and 64.4 ms after hydration (Figure 4B). Hydration reduced disagreement between the two methods, as reflected in narrower limits of agreement (fasting: −19.9 to 185.3 ms; hydrated: −7.3 to 136.2 ms). Nevertheless, the limits of agreement range remained wide for both, indicating that the methods show considerable variability. No evidence of proportional bias was observed, suggesting that the magnitude of the difference did not depend on the T1 value.

Figure 4 Agreement between wT1 and T1-MOLLI and segmental hydration effects. (A) Linear regression and correlation between mean T1-MOLLI and mean wT1 before and after hydration. A marker represents a volunteer. (B) Bland-Altman plot for T1-MOLLI and wT1 before hydration and Bland-Altman plot for T1-MOLLI and wT1 after hydration. (C) Grouped box plot for the whole cohort for the distribution of T1-MOLLI across S1, S2/3, S4a/b, S5/8, and S6/7 before and after hydration, demonstrating reduced apparent heterogeneity due to limited spatial coverage. (D) Grouped box plot for the whole cohort for the distribution of wT1 across all liver segments before and after hydration, showing variable hydration-induced increases across liver segments. SD, standard deviation; T1-MOLLI, T1-modified Look-Locker inversion recovery; VCTE, vibration-controlled transient elastography; wT1, water-specific T1.

A grouped box plot showed attenuated apparent heterogeneity of T1-MOLLI measurements between liver segments for both hydration states (Figure 4C). This reflects both the reduced spatial coverage of the single-slice T1-MOLLI acquisition and its limited sensitivity to segmental variation. In contrast, hydration-induced changes in wT1 at the segment level showed a wider dynamic range across Couinaud segments (Figure 4D). T1-MOLLI and wT1 increases due to hydration at the segment level are in accordance with the global hydration effects described above.

For T1-MOLLI, no statistically significant segment-wise differences between hydration states were observed (Table S3). In contrast, all wT1 segment-wise increases remained statistically significant after FDR correction (FDR-adjusted P<0.05), further highlighting the potential of wT1 to capture hydration-induced changes across the liver (Table S4).

Segmental variation within subjects in T1

The analysis of the spatial heterogeneity of T1-MOLLI and wT1 measurements demonstrated inter-segment differences for all participants, with wT1 showing a broader dynamic range than T1-MOLLI. Figure 5 shows representative T1-MOLLI (Figure 5A) and wT1 (Figure 5B) measurements before hydration for four participants. T1-MOLLI, limited to a single slice and restricted to the caudate lobe (S1) and four segmental junctions (S2/3, S4a/b, S5/8, S6/7), exhibited less apparent heterogeneity than wT1. The latter reflects the limited spatial sampling rather than accurate physiologic uniformity.

Figure 5 Variation across liver segments in four representative volunteers. (A) T1-MOLLI values before hydration from the five regions covered by the single-slice MOLLI acquisition (S1 and four segmental junctions: S2/3, S4a/b, S5/8, S6/7), demonstrating reduced apparent heterogeneity within each volunteer. (B) wT1 values before hydration from all nine Couinaud segments, illustrating physiologic inter-segment variability and broader range within volunteers compared with T1-MOLLI. Values are shown as mean ± SD per volunteer. T1-MOLLI, T1-modified Look-Locker inversion recovery; wT1, water-specific T1.

wT1 spatial heterogeneity of hydration response

SD and CV results (Table 2) quantitatively confirmed the observed within-subject segmental heterogeneity of wT1 measurements. Although heterogeneity metrics decreased after hydration, these reductions were not statistically significant (P value >0.05).

Comparing wT1 values across Couinaud segments between hydration states in each subject showed that wT1 captures variations associated with both hydration and spatial heterogeneity. Figure 6 illustrates the combined influence of baseline segmental variation and hydration-induced changes in wT1 for the same four representative volunteers of Figure 5. Remarkably, wT1 depicts both hydration effect and spatial heterogeneity for combinations of these effects: (I) low segmental variation and low hydration effect; (II) low segmental variation and high hydration effect; (III) high segmental variation and low hydration effect; and (IV) high segmental variation and high hydration effect (Figure 6A). Individual subject profiles of (I–IV) are displayed for better understanding in Figure 6B-6E, respectively. In each subject, wT1 values differed across liver segments in the fasting state and generally increased to varying degrees after hydration. The magnitude and distribution of these effects were subject-specific, demonstrating that physiologic segmental variability and hydration effects coexist and contribute jointly to the observed wT1 patterns.

Figure 6 Spatial heterogeneity of hydration-induced wT1 variation. (A) Comparison of the wT1 values before and after hydration and the segmental variations for four volunteers. Each marker represents the mean of the measurements per volunteer, and the ranges across liver segments are shown as gray lines. Markers close to the identity x=y show a low hydration effect, while short lines represent tight ranges, indicating low spatial heterogeneity. These cases depict different combinations of spatial heterogeneity and hydration effects: (I) low segmental variation and low hydration effect (rhombus); (II) low segmental variation and high hydration effect (cross); (III) high segmental variation and low hydration effect (square); and (IV) high segmental variation and high hydration effect (triangle). Comparison of wT1 measurements across liver segments between hydration states for the volunteer with (B) low segmental variation and low hydration effect, (C) low segmental variation and high hydration effect, (D) high segmental variation and low hydration effect, and (E) high segmental variation and high hydration effect. wT1, water-specific T1.

Discussion

This study demonstrates that liver wT1 is influenced by hydration state in healthy volunteers and exhibits spatial heterogeneity across Couinaud segments. Using an accelerated multi-slice wT1 technique, we observed consistent post-hydration increases in wT1; however, the magnitude of change varied substantially between segments and individuals. PDFF and T2* remained within normal ranges while liver stiffness measured by transient elastography changed within the physiological range, supporting the interpretation that the observed wT1 changes reflect physiological modulation rather than subclinical liver disease.

These findings extend prior work on hydration-related variability in hepatic T1. Earlier single-slice shMOLLI studies demonstrated that hydration prolongs liver T1, whereas glycogen loading shortens it, highlighting competing physiological influences (14). More recent work showed dose-dependent changes in wT1 after ingestion of an isotonic drink, despite stable PDFF (15). The present study advances this literature by applying a water-specific multi-slice wT1 approach that minimizes fat-related bias and enables direct assessment of segmental heterogeneity across the entire liver. In contrast to single-slice acquisitions, this approach captures regional differences in hydration response that would otherwise be obscured by limited spatial sampling.

Although conducted in healthy volunteers, the observed spatial heterogeneity has direct implications for the imaging of chronic liver disease. Couinaud segments represent functionally independent units with distinct vascular supply and drainage, providing a structural basis for regional differences in perfusion, extracellular volume, and susceptibility to patterns of fibrosis or congestion (21-24). Accordingly, diseases such as primary sclerosing cholangitis, metabolic dysfunction-associated steatotic liver disease (MASLD), cirrhosis, and viral hepatitis exhibit pronounced spatial heterogeneity, where single-slice techniques may underestimate or miss clinically relevant regional changes (25-28).

Our data show that even under controlled physiological conditions, wT1 varies substantially across liver segments, underscoring the importance of whole-liver, segment-resolved imaging for accurate longitudinal assessment. This variability may partly reflect the functional independence of Couinaud segments, which differ in portal venous inflow, arterial supply, and venous drainage (24). Consequently, hydration-related changes in perfusion, blood volume, and extracellular water distribution may not occur uniformly throughout the liver. Future studies investigating the influence of hepatic vascular anatomy and common vascular variants may further elucidate the physiological basis of these observations.

Compared with established noninvasive techniques, wT1 mapping occupies a distinct role. Transient elastography samples only a small tissue volume and provides no spatial information, while MR elastography offers volumetric stiffness assessment but requires dedicated hardware and predominantly reflects mechanical properties (1,19,29,30). In the present study, transient elastography was included to assess whether hydration-related physiological changes are reflected in LSMs in addition to T1-based MRI biomarkers. Conventional single-slice T1-MOLLI mapping is further limited by restricted coverage and susceptibility to fat, T2*, and B₁⁺ effects (5,7). Moreover, the reduced correlation between hydration states suggests greater variability of T1-MOLLI under changing hydration conditions (Figure 3B), consistent with its known sensitivity to physiological and technical confounders and its limited spatial sampling. The multi-slice wT1 technique addresses several of these limitations by enabling water-specific, B₁⁺-robust, segment-wise assessment within a single short breath-hold, supporting its utility as a physiologically meaningful and clinically practical quantitative biomarker (16). However, the slice thickness of the wT1 acquisitions (10 mm) was double that of the T1-MOLLI acquisitions (5 mm), which may have influenced the comparison because different sampling volumes can result in different partial-volume effects, particularly in the presence of hydration-related changes in hepatic blood volume. Importantly, wT1 and T1-MOLLI are not presented as interchangeable measurements and the observed differences between them should be interpreted in the context of their distinct sensitivities to fat and their different acquisition characteristics. The wT1 method has already been shown to be a more robust fibrosis biomarker than MOLLI and extracellular volume (ECV) in a cohort with diffuse liver disease (9). In addition, our findings suggest that wT1 may be sensitive to hydration-induced physiological changes at both the subject and liver-segment levels while enabling assessment of segmental heterogeneity across the liver.

These findings also emphasize the importance of physiological standardization in quantitative liver MRI. Hydration-induced wT1 changes were comparable in magnitude to effects reported in longitudinal and interventional studies and were spatially heterogeneous (14). Physiological factors such as hydration, glycogen, and vascular dynamics can modulate liver T1 within ranges comparable to or exceeding single-session repeatability (4). Moreover, although the minimal hydration-induced PDFF changes were consistent with previous studies in volunteers (15) and patients with hepatic steatosis (without diffuse liver disease) (31), the physiological mechanisms underlying the low impact of hydration on PDFF have not been widely explored. It would be of interest to determine whether similarly low hydration-induced PDFF effects hold in MASLD cases. Accordingly, hydration state and fasting or fluid intake should be standardized or documented, particularly in longitudinal or multicenter studies.

Several limitations warrant consideration. First, the cohort consisted exclusively of healthy volunteers, and hydration-related wT1 behavior may differ in chronic liver disease. Studies in larger cohorts will be needed to further investigate the proposed method’s ability to characterize focal liver changes. Second, the hydration paradigm was designed to elicit measurable effects and does not capture minor day-to-day fluctuations. Third, T1-MOLLI was acquired in a single slice, precluding direct multi-slice comparison of segmental heterogeneity. Furthermore, the relatively low PDFF range of the cohort limits the assessment of differences between T1-MOLLI and wT1 across varying levels of hepatic fat content. A more rigorous comparison would require the same liver coverage and slice thickness for T1-MOLLI and wT1, as well as evaluation across a wider range of PDFF values. Fourth, despite the high inter-reader reproducibility, manual ROI placement on T2*, PDFF, T1-MOLLI, and wT1 maps may introduce variability in the results. Registration of these parametric maps to anatomical clinical images, along with automated segmentation tools, could enable standardized ROI placement and reduce variability. Finally, all measurements were performed on a single 3T system from one vendor, and cross-platform reproducibility was not assessed.

In conclusion, liver wT1 is physiologically modulated by hydration and presents spatial heterogeneity across liver segments, even in the healthy liver. These findings support the need to account for physiological state and favor whole-liver, segment-resolved approaches when interpreting quantitative liver MRI, particularly in diseases characterized by regional involvement.

Conclusions

Hydration increases liver wT1, while segment-resolved mapping reveals substantial spatial variability across Couinaud segments, even in healthy individuals. These findings highlight the importance of physiological standardization and whole-liver quantitative MRI when interpreting liver T1 measurements. Multi-slice wT1 mapping may improve the assessment of regional liver physiology and provide a robust framework for future studies in diffuse liver disease.

Acknowledgments

None.

Footnote

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2026-0862/dss

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2026-0862/coif). E.H.M. reports that Klinikum Rechts der Isar provided travel support for conference attendance. Since 1st July 2026, she has been employed by Philips Market DACH. The work reported in this manuscript was conducted before this employment commenced. K.W. and M.D. are employees of Philips. Philips had no role in the study design, data acquisition, data analysis, data interpretation, or manuscript preparation beyond the individual contributions of the listed authors. D.C.K. has received research grant funding from Philips Healthcare at the Technical University of Munich (TUM). The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Ethics Committee of the Technical University of Munich (TUM) (No. 2024-550-S-SB) and informed consent was taken from all individual participants.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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