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The Potential of Iron Oxide Nanoparticle-Enhanced MRI at 7 T Compared With 3 T for Detecting Small Suspicious Lymph
Carlijn J A Tenbergen1, Ansje S Fortuin, Jack J A van Asten
1From the Department of Medical Imaging, Radboud University Medical Center, Nijmegen, the Netherlands (C.J.A.T., A.S.F., J.J.A.v.A., A.V., B.W.J.P., T.H., J.O.B., M.C.M., T.W.J.S.); Department of Radiology, Ziekenhuis Gelderse Vallei, Ede, the Netherlands (A.S.F.); Erwin L. Hahn Institute for MR Imaging, University of Duisburg-Essen, Essen, Germany (S.O., H.H.Q., T.W.J.S.); High-Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany (S.O., H.H.Q.); and Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany (S.O.).
Background:
Accurate detection of lymph node (LN) metastases in prostate cancer (PCa) is a challenging but crucial step for disease staging. Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) enables distinction between healthy LNs and nodes suspicious for harboring metastases. When combined with MRI at an ultra-high magnetic field, an unprecedented spatial resolution can be exploited to visualize these LNs.
Purpose:
The aim of this study was to explore USPIO-enhanced MRI at 7 T in comparison to 3 T for the detection of small suspicious LNs in the same cohort of patients with PCa.
Materials And Methods:
Twenty PCa patients with high-risk primary or recurrent disease were referred to our hospital for an investigational USPIO-enhanced 3 T MRI examination with ferumoxtran-10. With consent, they underwent a 7 T MRI on the same day. Three-dimensional anatomical and T2*-weighted images of both examinations were evaluated blinded, with an interval, by 2 readers who annotated LNs suspicious for metastases. Number, size, and level of suspicion (LoS) of LNs were paired within patients and compared between field strengths.
Results:
At 7 T, both readers annotated significantly more LNs compared with 3 T (474 and 284 vs 344 and 162), with 116 suspicious LNs on 7 T (range, 1-34 per patient) and 79 suspicious LNs on 3 T (range, 1-14 per patient) in 17 patients. For suspicious LNs, the median short axis diameter was 2.6 mm on 7 T (1.3-9.5 mm) and 2.8 mm for 3 T (1.7-10.4 mm, P = 0.05), with large overlap in short axis of annotated LNs between LoS groups. At 7 T, significantly more suspicious LNs had a short axis <2.5 mm compared with 3 T (44% vs 27%). Magnetic resonance imaging at 7 T provided better image quality and structure delineation and a higher LoS score for suspicious nodes.
Conclusions:
In the same cohort of patients with PCa, more and more small LNs were detected on 7 T USPIO-enhanced MRI compared with 3 T MRI. Suspicious LNs are generally very small, and increased nodal size was not a good indication of suspicion for the presence of metastases. The high spatial resolution of USPIO-enhanced MRI at 7 T improves structure delineation and the visibility of very small suspicious LNs, potentially expanding the in vivo detection limits of pelvic LN metastases in PCa patients.
Insights
Seven Tesla (7 T) ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI detects more small lymph node metastases in prostate cancer (PCa) patients than 3 T MRI. This advanced imaging technique improves visualization of small metastatic lymph nodes.
Area of Science:
- Oncology
- Radiology
- Medical Imaging
Background:
- Accurate detection of lymph node (LN) metastases is critical for prostate cancer (PCa) staging.
- Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) aids in distinguishing metastatic LNs.
- Ultra-high field MRI offers enhanced spatial resolution for visualizing LNs.
Purpose of the Study:
- To compare the efficacy of USPIO-enhanced MRI at 7 Tesla (T) versus 3 T for detecting small suspicious LNs in PCa patients.
- To evaluate the impact of field strength on LN detection and characterization.
Main Methods:
- Twenty PCa patients underwent both USPIO-enhanced 3 T and 7 T MRI examinations.
- Three-dimensional anatomical and T2*-weighted images were analyzed by two blinded readers.
- Readers annotated LNs suspicious for metastases, comparing number, size, and level of suspicion between field strengths.
Main Results:
- Significantly more LNs were annotated at 7 T compared to 3 T (474 vs. 344 and 284 vs. 162).
- 7 T identified more suspicious LNs (116) than 3 T (79), with a higher proportion of small LNs (<2.5 mm short axis).
- 7 T MRI demonstrated superior image quality, structure delineation, and higher suspicion scores for metastatic nodes.
Conclusions:
- 7 T USPIO-enhanced MRI detects more small suspicious LNs in PCa patients than 3 T MRI.
- Nodal size is not a reliable indicator of metastasis; small size is common.
- The high resolution of 7 T MRI enhances the detection of very small metastatic LNs, potentially improving staging accuracy.
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