Enhancement of abdominal structures on MRI at 1.5 and 3 T: a retrospective intraindividual crossover comparison

OBJECTIVE

To quantitatively compare the extent of enhancement of abdominal structures on MRI in an intraindividual fashion at 1.5 and 3 T.

METHODS

HIPAA-compliant, retrospective, longitudinal, intraindividual, crossover study, with waived informed consent, of consecutive individuals scanned at both 1.5 and 3 T closed-bore magnets using gadobenate dimeglumine during different phases of enhancement at tightly controlled arterial phase timing. Quantitative ROI measurements and qualitative sub-phase arterial phase assignments were independently performed by two radiologists. Qualitative discrepancies were resolved by a senior radiologist.

RESULTS

Final population included 60 patients [41 female and 19 male; age, 49.35 ± 18.31 years (range 16-81); weight, 78.88 ± 20.3 kg (range 44.5-136)]. Similar enhancement peak patterns were noted at both field strengths. Interobserver agreement of quantitative evaluations was substantial. Significantly higher amplitudes of enhancement peaks were noted for all abdominal solid organs during all phases at 3 T, except for the pancreas (p = 0.17-0.30). Significantly higher amplitudes of enhancement peaks of the abdominal aorta at 1.5 T were noted.

CONCLUSION

Similar peak patterns of enhancement for abdominal structures were observed at 1.5 and 3 T, with solid abdominal organs showing a higher percentage enhancement at 3 T, while unexpectedly higher aortic higher percentage enhancement was observed at 1.5 T.

KEY POINTS

• Similar enhancement peak patterns at both field strengths for studied abdominal structures. • Significantly higher percentage enhancement of most abdominal organs at 3 T. • Non-statistically significant trend of higher pancreatic percentage enhancement at 3 T. • Significantly lower abdominal aortic percentage enhancement at 3 T.

Abdominal vasculature in dynamic contrast-enhanced liver MRI at 3.0T: an intraindividual comparative study using gadoxetate disodium and gadofosveset trisodium

OBJECTIVES

To intraindividually compare gadoxetate disodium and gadofosveset trisodium regarding vessel contrast, image quality and vessel delineation in dynamic contrast-enhanced liver MRI at 3.0T.

METHODS

Twelve patients underwent 3.0T MRI twice (24 examinations) with a single dose of gadoxetate disodium and gadofosveset trisodium, respectively. Signal intensity in abdominal vessels and tissue was determined. Vessel-to-background ratio (VBR) was calculated for each vessel and dynamic phase. All images were evaluated by two radiologists regarding image quality, vessel delineation and anatomic variants or pathologies with digital subtraction angiography as the standard of reference.

RESULTS

Gadofosveset trisodium demonstrated a significantly higher VBR compared to gadoxetate disodium (arterial phase: 0.57±0.12 [SD] vs. 0.46±0.19; portal venous phase: 0.51±0.11 vs. 0.37±0.14; equilibrium phase: 0.48±0.10 vs. 0.31±0.13; p≤0.01). Image quality and vessel delineation were rated equal or better for gadofosveset trisodium in all cases. These differences were not significant for most vessel segments. All anatomic variants were correctly identified by both readers for both contrast agents.

CONCLUSIONS

Although gadofosveset trisodium provides a significantly higher vessel contrast at 3.0T, gadoxetate disodium is equivalent by qualitative measurements. Thus, gadoxetate-enhanced liver MRI at 3.0T enables reliable assessment of the upper abdominal vasculature with the additional benefit of hepatobiliary imaging.

Clinical utility of gadoxetate disodium-enhanced hepatic MRI for stereotactic body radiotherapy of hepatocellular carcinoma

PURPOSE

To investigate the utility of gadoxetate disodium-enhanced hepatic MRI (EOB-MRI) for stereotactic body radiotherapy (SBRT) to treat hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

We divided 30 HCC patients who underwent SBRT into group A (no change in their Child-Pugh score 6 months post-SBRT) and group B (increased score 6 months post-SBRT). EOB-MRI was performed before and 6 months after SBRT. We calculated the liver-spleen contrast (LSC) ratio for each radiation dose area on hepatobiliary phase scans (LSCbefore using images obtained before SBRT and LSCafter using images acquired after SBRT) and the weighted LSC (W-LSC) as: [(mean LSCbefore (0-30 Gy) × liver volume (0-30 Gy) + mean LSCbefore (30 Gy-) × liver volume (30 Gy-))/total liver volume]. Then we compared the W-LSC, percentage of the liver volume exposed to >20 Gy (V20), and mean liver dose in the two groups.

RESULTS

The LSCafter at 48, 40, and 30 Gy to the liver was statistically lower than the unirradiated area of the liver (p < 0.01). Univariate analysis showed that only W-LSC was significantly associated with group B (p = 0.02).

CONCLUSION

W-LSC was a useful parameter for predicting changes in hepatic function after SBRT.

Quantitative and qualitative comparison of 0.025 mmol/kg gadobenate dimeglumine for abdominal MRI at 1.5T and 3T MRI in patients with low estimated glomerular filtration rate

PURPOSE

To investigate the efficacy and adequacy of enhancement employing 0.025 mmol/kg of gadobenate dimeglumine at 1.5 Tesla (T), and to compare the extent of enhancement of this dosage between 1.5T and 3T systems.

MATERIALS AND METHODS

Our final population included 116 consecutive patients who underwent 0.025 mmol/kg gadobenate dimeglumine-enhanced abdominal MRI (78 men and 38 women; age, 64.1 ± 13.6 years). Sixty patients underwent imaging at 1.5T and 56 patients underwent imaging at 3T. Abdominal enhancement was evaluated qualitatively and quantitatively. The quality of enhancement was compared using Mann-Whitney U test. The percentage of enhancement of each organ was compared using Student t-test.

RESULTS

The mean quality rating of enhancement was at least "good" in all phases of enhancement for both 1.5T and 3T. There was a non-significant trend to higher mean ratings at 3T. The liver showed a 1.3-fold higher arterial-phase percentage of enhancement at 3T (p=0.0138). There were no differences between the mean relative enhancement of the pancreas and aorta throughout all phases of enhancement. The percentage of enhancement of the renal cortex was significantly higher at 3T (p<0.0001 to p=0.0293).

CONCLUSION

A dose of 0.025 mmol/kg of gadobenate dimeglumine demonstrates diagnostic enhancement in the majority of patients at 1.5T, without significant differences on qualitative evaluation compared to 3T.

Liver failure after major liver resection: risk assessment by using preoperative Gadoxetic acid-enhanced 3-T MR imaging

PURPOSE

To determine if gadoxetic acid-enhanced magnetic resonance (MR) imaging with measurement of relative liver enhancement (RLE) on hepatobiliary phase images can allow preoperative assessment of the risk of liver failure after major liver resection.

MATERIALS AND METHODS

The local institutional review committee approved this retrospective analysis and waived written informed consent. The study included 73 patients (39 men; median age, 64.4 years) who underwent gadoxetic acid-enhanced 3-T MR imaging before resection of three or more liver segments. RLE was calculated as the ratio of signal intensity measurements of the liver parenchyma before and 20 minutes after intravenous administration of gadoxetic acid. RLE was assessed in each liver segment and the mean value of all segments was used for analysis. Posthepatectomy liver failure was defined according to the "50-50 criteria" (ie, prothrombin time <50% and serum bilirubin >50 µmol/L on postoperative day 5) and the International Study Group of Liver Surgery (ISGLS) classification. The association of RLE and liver failure was tested with univariate and multivariate logistic regression analysis. In addition to RLE, the latter also included demographic, clinical, operative, and histologic variables.

RESULTS

Patients with liver failure according to the 50-50 criteria (n = 3) had significantly lower RLE (54.5%) than those without (125.6%) (P = .009). According to ISGLS criteria, RLE was 112.5% in patients with grade A liver failure (n = 20), 88.4% in patients with grade B (n = 7), 41.7% (n = 2) in patients with grade C, and 136.5% (P < .001) in those without liver failure. In a logistic regression analysis, RLE was inversely related to the probability of liver failure according to the 50-50 (P = .02) and ISGLS (P < .001) criteria. In a multivariate analysis, RLE was independently associated with a higher probability of liver failure according to ISGLS classification (P = .003).

CONCLUSION

Gadoxetic acid-enhanced MR imaging can help with the assessment of the risk for liver failure after major liver resection.

Time-intensity curve in the abdominal aorta on dynamic contrast-enhanced MRI with high temporal and spatial resolution: Gd-EOB-DTPA versus Gd-DTPA in vivo

PURPOSE

To evaluate the difference in the time-intensity curves (TICs) of the abdominal aorta on dynamic contrast-enhanced MRI (DCE-MRI) between Gd-DTPA and Gd-EOB-DTPA.

MATERIALS AND METHODS

Ten healthy volunteers underwent DCE-MRI three times with the following protocol: group A, Gd-DTPA at an injection rate of 3 ml/s; group B, Gd-EOB-DTPA, 3 ml/s; group C, Gd-EOB-DTPA, 1.5 ml/s. Signal intensities (SIs) of the abdominal aorta were measured, and the contrast enhancement ratio (CER) was calculated. Time-to-CER curves were compared among the three groups. The differences in maximum CER (CERmax) and time-to-peak of CER were analyzed.

RESULTS

The time-to-CER curve showed a double peak pattern in group A and single-peak pattern in groups B and C. The mean time between the first and the second peak was 6.2 s. The mean CERmax of each group was 4.50, 4.52 and 4.27, respectively. In group A, B and C, the mean time-to-peak was 14.6, 10.6 and 12.6 s, respectively. There was a significant difference between group A and B (P < 0.01).

CONCLUSION

To set up the optimal protocol for abdominal DCE-MRI, it should be noted that TIC in the Gd-DTPA and Gd-EOB-DTPA group showed different patterns, and a slower injection rate showed a less abrupt SI change in the Gd-EOB-DTPA group than in the Gd-DTPA group.