Abstract
PurposeTo evaluate the technical feasibility of high-resolution USPIO-enhanced magnetic resonance imaging of pelvic lymph nodes (LNs) at ultrahigh magnetic field strength.Materials and methodsThe ethics review board approved this study and written informed consent was obtained from all patients. Three patients with rectal cancer and three selected patients with (recurrent) prostate cancer were examined at 7-T 24–36 h after intravenous ferumoxtran-10 administration; rectal cancer patients also received a 3-T MRI. Pelvic LN imaging was performed using the TIAMO technique in combination with water-selective multi-GRE imaging and lipid-selective GRE imaging with a spatial resolution of 0.66 × 0.66 × 0.66mm3. T2*-weighted images of the water-selective imaging were computed from the multi-GRE images at TE = 0, 8, and 14 ms and used for the assessment of USPIO uptake.ResultsHigh-resolution 7-T MR gradient-echo imaging was obtained robustly in all patients without suffering from RF-related signal voids. USPIO signal decay in LNs was visualized using computed TE imaging at TE = 8 ms and an R2* map derived from water-selective imaging. Anatomically, LNs were identified on a combined reading of computed TE = 0 ms images from water-selective scans and images from lipid-selective scans. A range of 3–48 LNs without USPIO signal decay was found per patient. These LNs showed high signal intensity on computed TE = 8 and 14 ms imaging and low R2* (corresponding to high T2*) values on the R2* map.ConclusionUSPIO-enhanced MRI of the pelvis at 7-T is technically feasible and offers opportunities for detecting USPIO uptake in normal-sized LNs, due to its high intrinsic signal-to-noise ratio and spatial resolution.Key Points• USPIO-enhanced MRI at 7-T can indicate USPIO uptake in lymph nodes based on computed TE images.• Our method promises a high spatial resolution for pelvic lymph node imaging.
Highlights
Lymph nodes often are the first organs to which cancer metastasizes
The aim of this paper is to demonstrate the technical feasibility of 7-T high-resolution ultrasmall superparamagnetic particles of iron oxide (USPIO)-enhanced MRI of pelvic lymph nodes in patients with pelvic cancers
Normal lymph nodes, which show high USPIO uptake, appeared dark on the water-selective computed TE imaging at long TE due to the strong R2* decay effectuated by the USPIOs
Summary
Lymph nodes often are the first organs to which cancer metastasizes. Given its high sensitivity (82–96%) and specificity (93– 98%) [3,4,5,6,7], MRI in combination with a lymphotropic ultrasmall superparamagnetic particles of iron oxide (USPIO) contrast agent may be a valid non-invasive alternative for pelvic lymph node staging and has recently gained renewed interest [8, 9]. The sensitivity decreases to 41% for lymph nodes smaller than 5 mm [4]. These studies were performed on 1.5-T MR systems in the early 2000s [4]. A higher spatial resolution may allow a better identification of lymph node resembling structures such as nerve ganglia
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