Application of an advanced noise reduction algorithm for imaging of hands in rheumatic diseases: evaluation of image quality compared to standard-dose images.

OBJECTIVES: X-ray is the fundamental imaging technique in both diagnosis and follow-up of rheumatic diseases. As patients often require sequential X-rays over many years, dose reduction is of great importance. New advanced noise reduction algorithms allow for a dose reduction of up to 50%. The aim of this study was to evaluate whether quality of low-dose images is non-inferior to standard-dose images and, therefore, application of this technique is possible in the context of imaging of rheumatic diseases. METHODS: A total of 298 patients with known or suspected rheumatic disease were enrolled prospectively into this study, separated into three consecutive groups: 80%, 64% and 50% tube charge reduction. All patients received imaging of one hand (laterality randomly assigned) with low-dose technique and imaging of the contralateral hand with standard-dose protocol. Images were evaluated by two independent readers who scored (on a scale of 1-5) the visualization of bony cortex, trabeculae and joint spaces of fingers and wrist separately. Additionally, soft tissue and overall contrast were evaluated on the same scale. RESULTS: Overall image quality (expressed by mean sum score out of 40) of the 50% low-dose images was 31.52 (SD 1.94) vs. 31.66 (SD 1.82) for standard images (p = 0.068). Bony contours as well as trabeculae were equally well visualized in both image sets. Median scores for soft tissue visualization was slightly lower for low dose compared to standard images [4 (IQR 3.5-4) vs. 4 (IQR 3.88-4); p = 0.001]. CONCLUSIONS: Overall image quality of low-dose images was not inferior to standard-dose images. Therefore, the application of low-dose technology based on advanced noise estimation algorithms in the context of imaging of rheumatic diseases is possible.

Advantages of a T1-Weighted Gradient-Recalled Echo (GRE) Sequence With a Radial 3D Sampling Approach Versus 2D Turbo Spin-Echo and Cartesian 3D GRE Sequences in Head and Neck MRI.

OBJECTIVE. The purpose of this study is to compare the image quality, including artifacts, of a T1-weighted gradient-recalled echo (GRE) MRI sequence with a radial sampling approach to that of both 2D turbo spin-echo (TSE) and cartesian 3D GRE MRI sequences performed in the head and neck region. MATERIALS AND METHODS. The retrospective study included 26 datasets of patients who underwent MRI examination for inflammatory or neoplastic diseases of the head and neck region performed using a 1.5-T system. All examination protocols comprised three fat-saturated T1-weighted sequences performed in the axial plane after contrast agent administration. Axial FOV and spatial resolution in plane and along the z-axis were recorded. Sequences were evaluated independently by two readers for qualitative and quantitative parameters, including homogeneity of fat saturation and discrimination of pharyngeal wall structures. Qualitative parameters were evaluated using a 5-point Likert scale. RESULTS. For comparison, mean values of Likert scale scores were generated from the two readers' data. Fat saturation was significantly better on the radial GRE sequences (1.942) than on the TSE (2.346; p = 0.002) and cartesian GRE (2.365; p = 0.008) sequences. The overall impact of foreign material artifacts was comparable among sequences (radial GRE, 1.731; TSE, 1.731 [p = 1.000]; cartesian GRE, 1.769 [p = 0.414]); however, on direct comparison, the mean area that was not evaluable because of susceptibility was smaller on radial GRE sequences (53.8 mm) than on TSE sequences (59.8 mm; p = 0.062) and cartesian GRE sequences (59.6 mm; p = 0.079). Overall image quality was 1.635 with the use of radial GRE, 2.423 with TSE (p = 0.000), and 2.500 with cartesian GRE (p = 0.000). CONCLUSION. For imaging of the head and neck region, radial GRE has several advantages, including improved fat saturation and reduced extent of susceptibility artifacts, compared with TSE and cartesian GRE, leading to improved overall image quality.

Assessment of the extracellular volume fraction for the grading of clear cell renal cell carcinoma: first results and histopathological findings.

OBJECTIVES: To assess the potential of T1 mapping-based extracellular volume fraction (ECV) for the identification of higher grade clear cell renal cell carcinoma (cRCC), based on histopathology as the reference standard. METHODS: For this single-center, institutional review board-approved prospective study, 27 patients (17 men, median age 62 ± 12.4 years) with pathologic diagnosis of cRCC (nucleolar International Society of Urological Pathology (ISUP) grading) received abdominal MRI scans at 1.5 T using a modified Look-Locker inversion recovery (MOLLI) sequence between January 2017 and June 2018. Quantitative T1 values were measured at different time points (pre- and postcontrast agent administration) and quantification of the ECV was performed on MRI and histological sections (H&E staining). RESULTS: Reduction in T1 value after contrast agent administration and MR-derived ECV were reliable predictors for differentiating higher from lower grade cRCC. Postcontrast T1diff values (T1diff = T1 difference between the native and nephrogenic phase) and MR-derived ECV were significantly higher for higher grade cRCC (ISUP grades 3-4) compared with lower grade cRCC (ISUP grades 1-2) (p < 0.001). A cutoff value of 700 ms could distinguish higher grade from lower grade tumors with 100% (95% CI 0.69-1.00) sensitivity and 82% (95% CI 0.57-0.96) specificity. There was a positive and strong correlation between MR-derived ECV and histological ECV (p < 0.01, r = 0.88). Interobserver agreement for quantitative longitudinal relaxation times in the T1 maps was excellent. CONCLUSIONS: T1 mapping with ECV measurement could represent a novel in vivo biomarker for the classification of cRCC regarding their nucleolar grade, providing incremental diagnostic value as a quantitative MR marker. KEY POINTS: • Reduction in MRI T1 relaxation times after contrast agent administration and MR-derived extracellular volume fraction are useful parameters for grading of clear cell renal cell carcinoma (cRCC). • T1 differences between the native and the nephrogenic phase are higher for higher grade cRCC compared with lower grade cRCC and MRI-derived extracellular volume fraction (ECV) and histological ECV show a strong correlation. • T1 mapping with ECV measurement may be helpful for the noninvasive assessment of cRCC pathology, being a safe and feasible method, and it has potential to optimize individualized treatment options, e.g., in the decision of active surveillance.